While I don't completely disagree as CG Trader has its issues. I'll give feedback that isn't just slamming the company.
Your models aren't something usable really. Maybe if you were going to do some proxy work roughing out a level or something but even then it's not what buyers want.
From an artistic standpoint. Your textures are just the same texture on all surfaces, there's no attention to detail. They simply don't hold up to current day standards for games or architectural renderings and sites like Turbo Squid have a much larger selection of better quality models for free.
I actually don't sell here. I just enter the competitions when I'm interested but that isn't a valid reason in this case. You have a ways to go to improve your work.
Your models are very simple, some aren't textured and the ones that aren't don't have materials set up for rendering. They just aren't worth purchasing. I know that sounds harsh but it's more helpful than blaming the site no matter how true the criticism of CTG may be. I would recommend hanging out at sites like polycount forums, art station, etc. to learn all you can and improve your craft.