Outlook 2016/ 19 connectivity issues to Exchange 2019 server after CU12 update

[Garob]

Experiencing a stange issue after CU 12 . 

Can connect to the Exchange  server [Version 15.2 ‎(Build 1118.7)‎ ]  via ECP/ OWA but new profile 

attempts from Outlook clients fail and generate the below ASP error in the logs . 

The origianl update (GUI based) failed with an access to webconfig file. The second, CLi /update unattended updates passed off OK. I have seen solutions that have meant copying and replacing web.config in inetpublishing  , done , and the two sharedwebconfig locations withing exchange , done . 

Rebuilt the OAB ,  Remade IIS virtual directories and also autodiscover directory (Remove-AutodiscoverVirtualDirectory  ) , checked and remade the DNS records. Error below. Any advice greatfully recieved.   

Log Name: Application
Source: ASP.NET 4.0.30319.0
Date: 29/04/2022 12:16:10
Event ID: 1310
Task Category: Web Event
Level: Warning
Keywords: Classic
User: N/A
Computer: Acmemailsever.DOMAIN.local
Description:
Event code: 3006 Event message: A parser error has occurred. Event time: 29/04/2022 12:16:10 Event time (UTC): 29/04/2022 11:16:10 Event ID: 4b99acbb2057477685b64e4258a0020f Event sequence: 1 Event occurrence: 1 Event detail code: 0 Application information: Application domain: /LM/W3SVC/1/ROOT/Autodiscover-76-132957045702581882 Trust level: Full Application Virtual Path: /Autodiscover Application Path: C:\Program Files\Microsoft\Exchange Server\V15\FrontEnd\HttpProxy\Autodiscover\ Machine name: ACMEMAILSEVER Process information: Process ID: 17960 Process name: w3wp.exe Account name: NT AUTHORITY\SYSTEM Exception information: Exception type: HttpException Exception message: Could not load type 'Microsoft.Exchange.HttpProxy.ProxyApplication'.
at System.Web.Compilation.BuildManager.ReportTopLevelCompilationException()
at System.Web.Compilation.BuildManager.EnsureTopLevelFilesCompiled()
at System.Web.Compilation.BuildManager.CallAppInitializeMethod()
at System.Web.Hosting.HostingEnvironment.Initialize(ApplicationManager appManager, IApplicationHost appHost, IConfigMapPathFactory configMapPathFactory, HostingEnvironmentParameters hostingParameters, PolicyLevel policyLevel, Exception appDomainCreationException)

Could not load type 'Microsoft.Exchange.HttpProxy.ProxyApplication'.
at System.Web.UI.TemplateParser.ParseString(String text, VirtualPath virtualPath, Encoding fileEncoding)
at System.Web.UI.TemplateParser.ParseFile(String physicalPath, VirtualPath virtualPath)
at System.Web.UI.TemplateParser.ParseInternal()
at System.Web.UI.TemplateParser.Parse()
at System.Web.Compilation.BaseTemplateBuildProvider.get_CodeCompilerType()
at System.Web.Compilation.BuildProvider.GetCompilerTypeFromBuildProvider(BuildProvider buildProvider)
at System.Web.Compilation.BuildProvidersCompiler.ProcessBuildProviders()
at System.Web.Compilation.BuildProvidersCompiler.PerformBuild()
at System.Web.Compilation.ApplicationBuildProvider.GetGlobalAsaxBuildResult(Boolean isPrecompiledApp)
at System.Web.Compilation.BuildManager.CompileGlobalAsax()
at System.Web.Compilation.BuildManager.EnsureTopLevelFilesCompiled()

Could not load type 'Microsoft.Exchange.HttpProxy.ProxyApplication'.
at System.Web.UI.TemplateParser.ProcessException(Exception ex)
at System.Web.UI.TemplateParser.ParseStringInternal(String text, Encoding fileEncoding)
at System.Web.UI.TemplateParser.ParseString(String text, VirtualPath virtualPath, Encoding fileEncoding)

Could not load type 'Microsoft.Exchange.HttpProxy.ProxyApplication'.
at System.Web.UI.TemplateParser.GetType(String typeName, Boolean ignoreCase, Boolean throwOnError)
at System.Web.UI.TemplateParser.ProcessInheritsAttribute(String baseTypeName, String codeFileBaseTypeName, String src, Assembly assembly)
at System.Web.UI.TemplateParser.PostProcessMainDirectiveAttributes(IDictionary parseData)

Request information: Request URL: https://acmemailsever.domain.local:443/Autodiscover/Autodiscover.xml Request path: /Autodiscover/Autodiscover.xml User host address: 192.168.0.119 User: Is authenticated: False Authentication Type: Thread account name: NT AUTHORITY\SYSTEM Thread information: Thread ID: 6 Thread account name: NT AUTHORITY\SYSTEM Is impersonating: False Stack trace: at System.Web.Compilation.BuildManager.ReportTopLevelCompilationException()
at System.Web.Compilation.BuildManager.EnsureTopLevelFilesCompiled()
at System.Web.Compilation.BuildManager.CallAppInitializeMethod()
at System.Web.Hosting.HostingEnvironment.Initialize(ApplicationManager appManager, IApplicationHost appHost, IConfigMapPathFactory configMapPathFactory, HostingEnvironmentParameters hostingParameters, PolicyLevel policyLevel, Exception appDomainCreationException)
Custom event details:
Event Xml:
<Event xmlns="http://schemas.microsoft.com/win/2004/08/events/event">
<System>
<Provider Name="ASP.NET 4.0.30319.0" />
<EventID Qualifiers="32768">1310</EventID>
<Level>3</Level>
<Task>3</Task>
<Keywords>0x80000000000000</Keywords>
<TimeCreated SystemTime="2022-04-29T11:16:10.325154500Z" />
<EventRecordID>8602147</EventRecordID>
<Channel>Application</Channel>
<Computer>Acmemailsever.DOMAIN.local</Computer>
<Security />
</System>
<EventData>
<Data>3006</Data>
<Data>A parser error has occurred.</Data>
<Data>29/04/2022 12:16:10</Data>
<Data>29/04/2022 11:16:10</Data>
<Data>4b99acbb2057477685b64e4258a0020f</Data>
<Data>1</Data>
<Data>1</Data>
<Data>0</Data>
<Data>/LM/W3SVC/1/ROOT/Autodiscover-76-132957045702581882</Data>
<Data>Full</Data>
<Data>/Autodiscover</Data>
<Data>C:\Program Files\Microsoft\Exchange Server\V15\FrontEnd\HttpProxy\Autodiscover\</Data>
<Data>ACMEMAILSEVER</Data>
<Data>
</Data>
<Data>17960</Data>
<Data>w3wp.exe</Data>
<Data>NT AUTHORITY\SYSTEM</Data>
<Data>HttpException</Data>
<Data>Could not load type 'Microsoft.Exchange.HttpProxy.ProxyApplication'.
at System.Web.Compilation.BuildManager.ReportTopLevelCompilationException()
at System.Web.Compilation.BuildManager.EnsureTopLevelFilesCompiled()
at System.Web.Compilation.BuildManager.CallAppInitializeMethod()
at System.Web.Hosting.HostingEnvironment.Initialize(ApplicationManager appManager, IApplicationHost appHost, IConfigMapPathFactory configMapPathFactory, HostingEnvironmentParameters hostingParameters, PolicyLevel policyLevel, Exception appDomainCreationException)

Could not load type 'Microsoft.Exchange.HttpProxy.ProxyApplication'.
at System.Web.UI.TemplateParser.ParseString(String text, VirtualPath virtualPath, Encoding fileEncoding)
at System.Web.UI.TemplateParser.ParseFile(String physicalPath, VirtualPath virtualPath)
at System.Web.UI.TemplateParser.ParseInternal()
at System.Web.UI.TemplateParser.Parse()
at System.Web.Compilation.BaseTemplateBuildProvider.get_CodeCompilerType()
at System.Web.Compilation.BuildProvider.GetCompilerTypeFromBuildProvider(BuildProvider buildProvider)
at System.Web.Compilation.BuildProvidersCompiler.ProcessBuildProviders()
at System.Web.Compilation.BuildProvidersCompiler.PerformBuild()
at System.Web.Compilation.ApplicationBuildProvider.GetGlobalAsaxBuildResult(Boolean isPrecompiledApp)
at System.Web.Compilation.BuildManager.CompileGlobalAsax()
at System.Web.Compilation.BuildManager.EnsureTopLevelFilesCompiled()

Could not load type 'Microsoft.Exchange.HttpProxy.ProxyApplication'.
at System.Web.UI.TemplateParser.ProcessException(Exception ex)
at System.Web.UI.TemplateParser.ParseStringInternal(String text, Encoding fileEncoding)
at System.Web.UI.TemplateParser.ParseString(String text, VirtualPath virtualPath, Encoding fileEncoding)

Could not load type 'Microsoft.Exchange.HttpProxy.ProxyApplication'.
at System.Web.UI.TemplateParser.GetType(String typeName, Boolean ignoreCase, Boolean throwOnError)
at System.Web.UI.TemplateParser.ProcessInheritsAttribute(String baseTypeName, String codeFileBaseTypeName, String src, Assembly assembly)
at System.Web.UI.TemplateParser.PostProcessMainDirectiveAttributes(IDictionary parseData)

</Data>
<Data>https://acmemailsever.domain.local:443/Autodiscover/Autodiscover.xml</Data>
<Data>/Autodiscover/Autodiscover.xml</Data>
<Data>192.168.0.119</Data>
<Data>
</Data>
<Data>False</Data>
<Data>
</Data>
<Data>NT AUTHORITY\SYSTEM</Data>
<Data>6</Data>
<Data>NT AUTHORITY\SYSTEM</Data>
<Data>False</Data>
<Data> at System.Web.Compilation.BuildManager.ReportTopLevelCompilationException()
at System.Web.Compilation.BuildManager.EnsureTopLevelFilesCompiled()
at System.Web.Compilation.BuildManager.CallAppInitializeMethod()
at System.Web.Hosting.HostingEnvironment.Initialize(ApplicationManager appManager, IApplicationHost appHost, IConfigMapPathFactory configMapPathFactory, HostingEnvironmentParameters hostingParameters, PolicyLevel policyLevel, Exception appDomainCreationException)
</Data>
</EventData>
</Event>