I used to be able to connect to the bedrock server just fine, but it suddenly stopped working.

https://bedrockinfo.com/ can connect fine and displays the correct server info, but my iOS clients just say "can't connect to the world".

Restarting the server nor the clients does not help. 

I upgraded to 1.16.100 and the issue persist.

It's running on Ubuntu, there is no firewall set-up. I can't even connect by typing local IP within the same network.

How can I troubleshoot further? How to get more debug info from the iOS client?

How to get the server to be more verbose? It does not show anything in the log file when https://bedrockinfo.com/  is sending requests.