In Event Viewer > Windows Logs > Application, you notice an event with ID 3277 having "ENDPOINT_NOT_FOUND" in its description. Which of the following is the possible reason for this issue?

Answer options:

A.There is no VM in your host pool.
B.The virtual machines in your host pool are not active.
C.All virtual machines in your host pool have crossed the max session limit.
D.None of the virtual machines in your host pool has the agent service running on it.
E.Any of the above

Correct Answer: E 
Go to Event Viewer -> Windows Logs -> Application. If you notice an event with ID 3277 that states "ENDPOINT_NOT_FOUND" in its description it means the broker could not find any endpoint to make a connection with. This connection related problem might happen due to any one of the below reasons: There are no virtual machines in your host pool
The virtual machines in your host pool are not active
All virtual machines in your host pool have crossed the max session limit
No virtual machine in your host pool has the agent service running on it
Option A is incorrect. The connection issue may arise because of any one of the given reasons.
Option B is incorrect. One of the possible reasons for the connection issue is "the virtual machines in your host pool are not active”. Other given options are also valid reasons.
Option C is incorrect. One of the possible reasons for the connection issue is "All virtual machines in your host pool have crossed the max session limit”. Other given options are also valid reasons.
Option D is incorrect. The given one is also one of the valid reasons but other options are also valid.
Option E is correct. The connection issue may arise because of any one of the given reasons.
Reference: 
To know more about how to troubleshoot common Azure Virtual Desktop Agent issues, please visit the below-given link: 

https://docs.microsoft.com/en-us/azure/virtual-desktop/troubleshoot-agent