Bought two prime accounts. Seller gave two emails/passwords. When I tried signing into them on twitch, I got an error saying email sign in was disabled and to use the twitch username instead. Asked seller what the usernames were, he said he could not provide them, and that the accounts worked...
Big vouch for Giggs, I was having issues activating prime (seemed to be an issue on my end), gave him my account details and he got it activated in less than a minute.