WoW - can't purchase guild charter

As title says, once I enter the guild name and click purchase (Stormwind), the window just closes - silver isn’t deducted, nor does the charter appear in the inventory.

I’ve tried deleting cache, restarting both the client and computer, logging in with a different character.

I’ve tried entering various guild names (even ones that already were taken) - no error message or anything else appears - the window just closes without any changes.

I’m not using any addons.

I’ve literally just purchased the subscription and if I may be completely frank - feels like I’ve made a mistake.