How I lost $4M by simply using MEXC

Im basically never using CEX usually, Im mostly using p2p over the years. But ive had quite a nice real estate deal and i needed to sell some BTC for USDT fast so I decided to use MEXC as here, everybody uses it, full KYC done, everything clean. The moment I deposited, funds got locked instantly, cant trade, cant withdraw, nothig..

Its been 3 weeks now, support going in circles asking for proof of funds I just dont have (old p2p coins from 2015/etc, while i provided as much documents as i have). Deadline is coming and I might lose the deal over this. Been reading over reddit and seems it happens a lot. Anyone managed to unlock in a similar situation? Should I que then? advices appreciated