Just in case it matters: My account is based in Steam not downloaded client from the site.
I used my OG character to buy 1000 Aurum from the store and then I logged back to the Character select, hit the “Buy character slot button” got the confirmation screen “Do you wish to use this much to buy a character slot” Hit yes and nothing happened. It’s just my one character. the 1000 Aurum is gone and I’m not sure what to do if it worked or if there was a glitch and I’m owed a slot/my aurum back.
You’ll probably want to send a http://help.funcom.com petition, because they can take care of account and payment issues there. Exactly how long you might be waiting, that’s up in the air. Timeliness isn’t exactly their strong suit nowadays, sadly.
Yep, as Aeryl said, you’ll have to completely restart the client. You won’t see it until you do, even if you logged in and out of another character or managed to reload the UI.