Not sure what the game is your giving away. A lot of people are making accounts just to give away games that are free from other websites (Heck some are free from this website) And those aren't allowed . If you recieved that game free from another website (for instance if it is on this list
https://www.reddit.com/r/FreeGamesOnSteam/ ) Then those games are not allowed .. you will see some get away with it for now but those problems will slowly be fixed. Although some will sneak through the cracks do you want to do all the work only to have your account banned later??
ok if that is not the case understand once again website is in Beta. so there are glitches everywhere try a different browser, Clear cache , And if you can't find an easy solution email support. you may not hear back but they will put that on their "To Check List" and on the next site update Hopefully fix that problem.