Try using next.nostrudel.ninja to see if it works.
Try changing the notification type in amber to direct connection or enabling tor
Discussion
Also check if you enabled network permission in amber
Nothing happens after I granted permission. 
It stack like this in amber and nostrudel just saying connecting 
I see. I think you are having some connection issue with the relay.
I'll try to improve this
Try restarting your vpn if you are using one
Try deleting the app in amber and creating a new one, after that add one more relay like relay.damus.io
Copy the new bunker url and try logging into nostrudel again