My Apple Watch SE is stuck on the "Update Complete" screen

Press and hold both the side button and digital crown, then release both buttons when you see the Apple logo. Wait a few seconds, then hold down just the side button until you see the "erase all settings" prompt on the screen, then erase all your settings. Remember, you can pair your Watch again with a backup if you have so.

-Zachyy ✌️

Just press the dismiss button or the Digital Crown 😊

I had the same problem and sometimes you can reset all settings on your iPhone and it refreshes the connection etc and hope this helps

Glad to hear.