New server - insufficient permission modify power

I’ve just installed teamspeak server on a ubuntu 18 vps, entering the privilege key I get from that install works fine and gives me the ‘Server Admin’ group, however whatever I try, I am not allowed to edit the ‘Global’ permissions for any group, which results in the error as seen in the title. It doesn’t really make sense considering I’ve changed those permissions before to my knowledge and it’s a completely fresh/new server as well.
Gif: Imgur
Error message: