In OP's words: "they won't take it as a source of funds", so i'm guessing that for him to write that, he has presented Kucoin with proof from the freelance job he does, and it was rejected. Centralized exchanges can be very difficult in situations like this, and passing their request can even prove impossible sometimes.
He can ask them why they rejected the proof of source of funds he sent them. They may be rejecting the screenshots because they can be edited or faked. Maybe they want him to make a screen recording of the freelance platform and the withdrawal page, showing the amount he withdrew, the withdrawal date, the wallet address he sent the funds to and anything else that can prove where the funds came from.
I had a friend who had a similar issue on MEXC and in the end, after many attempts and more than two weeks, they accepted what he provided and let him withdraw after he submitted all the proof they needed.
The problem here is that they don't have a specific timeframe for the manual review, so following up with them through their official channels may be a good way to get their attention and have them review the case ASAP.
