Released: April 2021 Exchange Server Security Updates

After this update our support tool does not work any more. We run a exchange 2016 server, and the tool does a simple:

        public void SearchExchangeMailBox()
        {
           
            PSCredential cred = new PSCredential(ADtoolUserName, ADtoolUserPassword);
            WSManConnectionInfo connectionInfo = new WSManConnectionInfo(new Uri("http://exch01/powershell?serializationLevel=Full"), "http://schemas.microsoft.com/powershell/Microsoft.Exchange", cred);
            connectionInfo.AuthenticationMechanism = AuthenticationMechanism.Kerberos;




                using (Runspace runspace = RunspaceFactory.CreateRunspace(connectionInfo))
                {

                        using (PowerShell powershell = PowerShell.Create())
                        {

                            powershell.AddScript("Get-Mailbox " + SelectedUsername + "*");
                            runspace.Open();
                            powershell.Runspace = runspace;

                            Collection<PSObject> results = powershell.Invoke();
                            foreach (ErrorRecord err in powershell.Streams.Error)
                            {
                                MessageBox.Show("Error");
                                MessageBox.Show(err.ToString());
                            }

But that now throws a error now. Nothing has change on our part. 

System.Management.Automation.RemoteException: The syntax is not supported by this runspace. This can occur if the runspace is in no-language mode.
   ved System.Management.Automation.Runspaces.AsyncResult.EndInvoke()
   ved System.Management.Automation.PowerShell.CoreInvokeRemoteHelper[TInput,TOutput](PSDataCollection`1 input, PSDataCollection`1 output, PSInvocationSettings settings)
   ved System.Management.Automation.PowerShell.CoreInvoke[TInput,TOutput](PSDataCollection`1 input, PSDataCollection`1 output, PSInvocationSettings settings)
   ved System.Management.Automation.PowerShell.Invoke(IEnumerable input, PSInvocationSettings settings)
   ved ADTool.MainForm.SearchExchangeMailBox()
   ved ADTool.MainForm.searchBtn_Click(Object sender, EventArgs e)
   ved System.Windows.Forms.Control.OnClick(EventArgs e)
   ved System.Windows.Forms.Button.OnClick(EventArgs e)
   ved System.Windows.Forms.Button.PerformClick()
   ved ADTool.MainForm.searchBox_KeyUp(Object sender, KeyEventArgs e)
   ved System.Windows.Forms.Control.OnKeyUp(KeyEventArgs e)
   ved System.Windows.Forms.Control.ProcessKeyEventArgs(Message& m)
   ved System.Windows.Forms.Control.WmKeyChar(Message& m)
   ved System.Windows.Forms.Control.WndProc(Message& m)
   ved System.Windows.Forms.TextBox.WndProc(Message& m)
   ved System.Windows.Forms.NativeWindow.Callback(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam)