Unable to connect to session hosts

[Mark_Millington]

Some of our users mainly Europe are experiencing issues with connecting to our AVD installation. Nothing has changed but users now receive "An error occurred while accessing this resource. Retry the connection or contact your System administrator."

Error code 0x3000047

Extended error code 0x0

If I look at the insights page and lookup a user I see the following error. 

Kind: Deployment

Source: RDStack

Error: ReverseConnectFailed (24)

Message Sample: The session host couldn't connect to the Windows Virtual Desktop Service due to an unexpected network failure. 

Any pointers would be much appreciated as I can't find anything on-line.

[#2]

Are all session hosts Available? This usually points to the network appliance you are routing through being an issue. Make sure nothing is being blocked.

[#3]

@KevHal all session hosts are available and we have not made any changes to routing.  The networking side of the host pool is set to Enable public access for end users, use private access for session hosts. 

[#4]

@Mark_Millington 

Refer this may help:

https://techcommunity.microsoft.com/t5/azure-virtual-desktop/error-when-connecting-to-mvd-0x3000047/...