Go to Watch App > Me > Notification > Toggle Notification.
If you still don't receive notification, please re-toggle and reopen the Watch App.
If you want to mute or unmute some chats, please do it in the Telegram app, as it will take effect in the Watch App.
Make sure your network connection to Telegram is stable.
Reopen the Watch App to retry.
Relogin your Telegram account on the Watch App.
Open official 'Watch' App on iPhone.
Scroll down to the list of available applications.
Check and install the WatchGram app.
Swipe up the keyboard to switch between different languages.