This operation returned because the timeout period expired. (Exception from HRESULT: 0x800705B4)

I am facing an issue in getting channel URI for push notification in UWP.

 var channel = await PushNotificationChannelManager.CreatePushNotificationChannelForApplicationAsync();

Tried all answers given in StackOverflow and windows forums. Please help me in resolving this!!

Since your description was not detailed, and you just provided one line code. So, I'm not sure where the issue is. You need to do troubleshooting.

The How to request, create, and save a notification channel shows:

Handling errors in channel requests: The call to the createPushNotificationChannelForApplicationAsync method can fail if the Internet is not available. To handle this, add retry logic to the code shown in step 2. We recommend three attempts with a 10-second delay between each unsuccessful attempt. If all three attempts fail, your app should wait until the next time the user launches it to try again.

So, please check if your internet is available. An easy way is to download another one app from the Microsoft store to see if you can receive their app's notification.

Then, you might need to check your firewall to see if you allow your app through the windows firewall.

If you follow the complete steps on the Windows Push Notification Services (WNS) overview, in general, it would work.