Hmm. Perhaps something got borked server-side in the leadership shuffle? My only advice would be to get Lillu to look at it and assign L to the toon that needs it, then try again

In my case, it was the fact we had 2 leaders, which is apparently a UF feature unsupported by the server code, so one of the leaders (me) was denied access to those rights. (couldn't demote myself, pass leadership, set bankers, couldn't even disband myself from guild) The other toon (I logged him in, that toon was the original sole leader of the guild) was able to perform all functions normally.
Perhaps when development slows down, someone can look into tweaking this?

Hope you get it worked out, guild bankers is a horrible feature to lose (after I got used to it, I loved it

)