I've bought RK on Wednesday, received activation code, everything was fine.
I had to reenter the code each time after a longer break. It eventually stopped working. I get a "This access code is incorrect. Enter your email address to retrieve the correct code." message. Resending code doesn't work as I get same code. Code worked again on Thursday, twice, then stopped completely.
I've cleared cookies, tried in other browser, on other device, with no effect.
It's problem with the code/site itself.
I've created ticket #5716 but no response yet.