I bought a key about 24 hours ago, and i keep getting the 'key is invalid' message. I have emailed support and they said that the key is fine and to post on forums or ask discord for help. I have replied to a thread on here and asked a few people in discord with no help. Either would like a refund or help asap.
I didn't receive my key for about 3-4 days have had an email correspondence with support. Pretty disappointed with the whole ordeal, they finally emailed me a key and it's invalid. Attempting to do anything on buddyauth gives me a runtime error so now I'm going to be waiting another 12 hours for support to respond. Pretty awesome stuff.
Try switching your region at the log in screen. There was another post where it seems to have worked for a few people.