I still have a pending case with COSS exchange, I made a deposit and the deposit never showed in my COSS account,. This was in 2018 and when I wrote to support, after taking a very long time to respond, they still didn't resolve the issue up till today, I would rather throw a token away than trade it in COSS exchange, that's how much I dislike it.
Contact the new team they are much better at responding and fixing issues. You can directly message @Satyarth on telegram and he will get back to you asap