Hm, I'm not sure what could cause your plugin to work on all servers but one. But this indicates it is a problem with server specific files. Is this problem on all your chars on that server or only a specific one? Because some years ago I used a plugin that would help track your virtue deeds and every now and then the char files for the plugin would get corrupted, but only for one or two chars. I then went and deleted the plugin's sub-directory of server-name/char-name/<all files that could possibly belong to that plugin> or rather moved those files to a directory outside the lotro directory structure. Then the plugin would load as if it had never been used before.
I don't know if this will help, it's just how I try to tackle problems like this.
There's some good in this world, and it is worth fighting for.