The "Waiting for: System Event Notification Service" message typically appears when Windows is shutting down or restarting. In your case, if the message is appearing when you are trying to log out, it is possible that the System Event Notification Service (SENS) is not responding properly.
Here are a few steps you can try to resolve the issue:
1. Restart the SENS service: Press Windows + R, type "services.msc" and press Enter. Scroll down to the System Event Notification Service and right-click on it. Click "Restart" to restart the service.
2. Disable and enable SENS service: In the same Services window, right-click on System Event Notification Service and click "Properties". Change the startup type to "Disabled" and click "Apply". Restart the computer. After the restart, change the startup type back to "Automatic (Delayed Start)" and click "Apply".
3. Check for pending updates: Run Windows Update and make sure all updates are installed. Restart the computer and see if the issue persists.
4. Check for malware: Run a full system scan with your antivirus program to check for any malware or viruses that may be causing the issue.
5. Create a new user profile: Create a new user profile with administrative privileges and check if the issue occurs when logging out from the new profile.
If none of the above steps work, you may need to perform a system restore or reinstall the operating system. Before doing so, make sure to back up any important data on the server.