Hi
in my experience there are a few things that often go wrong when moving from one server to another and also changing the system/OS/config at the same time:
Firstly make sure all the system requirements are in place
xot.xerte.org.uk/play.php?template_id=81#systemrequirements
Also that the directory ownership and permissions are correct e.g. easiest way is to make sure the apache user has ownership and write access to everything.
If it's a new server and new install of MySQL/MariaDB make sure the Xerte db user has full permissions and that the credentials match or are updated
You don't mention what you are using for authentication but by the fact that you see a login screen I'm guessing it's db authentication or Ldap authentication and probably the latter. If so make sure any DNS/Firewall rules allow the relevant communication and make sure the LDAP PHP extension is enabled and mappings still correct.
Possibly the most likely thing is that the directory paths on the new server have changed and if so there are values in the db that need to be changed accordingly. Typically there are two path values that would need to be corrected/updated.
I have to add that it always alarms me to hear about broken installations due to server moves. All of that should be tested first with a test server and test installation. Perhaps that's the case here but the fact that you mention you installation is broken - Help suggests perhaps it's the production server that is broken?
If the above doesn't work and you need urgent help I work directly with organisations all the time but I'm afraid that time is chargeable.
HTH
Ron