The error message Invalid groupID comes when there is an user on the server with a Server Group or Channel Group that doesnt exist (because it was deleted for example). That means, the non-existent group / group ID need to be taken away from this user or the users, or an existing group / group ID need to get assigned.
Do this with the right mousebutton at the appropriate user or users with the assign Server Groups and assign Channel Group menus.
This is also possible of course with the ServerQuery, but is only recommended if you are familiar with it.