Are you running any mods perhaps?
If so i suggest you to test them one by one to see which one is a faulty one / not updated.
Make sure if you do tick them off, put the name of the mod in a note pad so you still have the name of the mod in case it is not that mod doing so. Make sure to REMOVE the mod from the list. Restart the server. There could be 1 mod or multiple that are out dated causing the server either not to load, restart loop or simple not going online.
If all mods has been tested and you have also removed them from the mod list while still encountering the same problem i suggest you to either roll back to your previous back up, if this doesn't seem to work, you might have to start clean again by reinstalling the server.
When the server does work after that you can put the mods 1 by 1 in and restart to check them out if they work. Some mods requires to be in order placed in order for them to work.
IF even after a clean instillation does not work you might want to fill out a support ticket with this issue and confirming them that you have done those actions. They can look up into the data base on what's truly going on.
If you wish and you do have mods enabled feel free to let me know what kind of mods and i could test them out for you as well.
Hope this helps!