If you cannot access the settings of the server that’s running on a machine when accessing it through that server’s IP address you probably got something wrong with some hidden plex settings. Did copy/clone the original server when creating the new on on Manjaro?
If so, this could cause some collisions (e.g. because the transferred preferences.xml file includes references to the old server’s machine identifier – this will result in both servers claiming to be the same machine)
Alternatively you could take a look at how to get back into a server if you accidentally locked yourself out
https://support.plex.tv/articles/204281528-why-am-i-locked-out-of-server-settings-and-how-do-i-get-in/