I did not look extensively there and obviously I did not see the CMS itself, only the login page.
The only thing that must be done though is to offer your customers the Xibo source code (or offer of it) and your customers must know that they are using open source software distributed under AGPLv3 licence - basically this Open Source Xibo
If it’s working locally, then I’d say it will be something in the php settings on your ‘live’ server or some other configuration issue, are all devices connected to that CMS experience similar problems?
Perhaps @dan would have a better idea of the error you’re seeing and what may have caused it.