@MyPhoneRobot: I sent you an email explaining what happened.
When a service inside an app that's published (web or native) uses the proxy, we do a check to make sure the app (the actual project) exists. This is to ensure we don't end up with apps published that use the proxy, but the actual app doesn't exist in Appery.io any more (the user might have cancelled the account).
If the app is deleted, then the check fails and the proxy will not work. We are going to add a check/warning when an app is deleted and it uses the proxy.
If Appery.io proxy is not used, then this is not a problem. The original app can be deleted.
To fix this issue, the app needs to be restored from backup and republished.