Hier zur Info aus dem US Forum:
Hi everyone,
There’s currently a bug that’s preventing some guilds from upgrading their guild when your guild has 10 ranks defined. We’re working on fixing this asap, but in the meantime would like to share a workaround: go to your Roles tab and delete one of those ranks; you should then have 9 ranks) and be able to upgrade again.
Sorry about that and thanks for your understanding!
https://forum-en.gw2archive.eu/forum/support/bugs/Issues-with-the-guild-system-please-post-here-MERGED/page/3