Can't sell some games on Glyde?

I use Glyde a lot to sell games I've beaten and won't play again. I don't mind losing a few dollars for the convenience of having the mailer sent to me rather than having to go to a physical store or ship via UPS or something. Recently, however, I've noticed that Glyde won't let me sell some games (e.g. Halo 5 or Rise of the Tomb Raider) because they simply don't show up in their "sell" search results. Anyone know why Glyde won't let you sell some games? I've emailed their support but have not gotten a response.

I wasn't even aware they were still around.

Maybe they forgot they still existed too.

Glyde has really tanked. I strongly recommend Gameflip. Same concept, but it's all done on mobile and very user-friendly.