I deployed an aaPanel instance from our Marketplace Apps to see if I could recreate this. I was able to break access to my panel, I wasn't able to get the exact same error, so I can't say for sure this will resolve your issue, but here are some suggestions.

If you're not able to reach the service over port 8888 (mine was set to port 7800 by default), then you should log in to your server over SSH to troubleshoot. Once logged in, you can run the following command to see what services are listening on which ports.

ss -plunt

If you see nothing is listening on 8888 (or 7800), then you'd need to start the service that's supposed to be listening.

I tried using systemctl but that wasn't working as it usually does, so I looked up how to start services in aaPanel. I found this aaPanel Forum post that discusses restarting php. I used the same logic there and applied it to the other services that should be running. For my instance, bt should be running on port 7800, so I ran this:

/etc/init.d/bt start

You can now use ss -plunt again to be sure that the service is running and on what port. Make sure you use the correct port when logging in.

This did get my panel back up, but again, I wasn't seeing the same NGINX error.

You might need to restart Apache or another service instead. You can use the ls command to see all the services in /etc/init.d/ and see if any aren't running when you use the ss command and try to restart anything that's missing.

If NGINX is using the port Apache is trying to use, that could also be a problem, so you may need to kill any NGINX processes that are running.

If this doesn't help, you may want to look into the forum for aaPanel since questions there will be focused on the same services. We're happy to try to help, but they may be better able to answer your questions there.

Thank you for answering, you made my day :)