I think you made a mistake by doing the mixer service and then using an exchange wallet. It is clear that centralized exchanges have a rule of not accepting deposits from the results of the mixer service because this violates their rules which they consider to be money laundering.
I have used the Mixer service several times but never sent it directly to a centralized exchange because I knew it would be dangerous if it was detected and the balance would be held, use another wallet to be safer, but this is not entirely YoMix's fault because the Uphold exchange itself has strict regulations.
Mixing is actually not money laundering, they're wrong to think it's a money laundering.
There's no different for using another wallet, it's a
concealing and they can easily recognize if the funds was come from mixing service.
How do mixers work? Do they use system similar to P2P if the number of coins of multiple users match each-other? Then it can create serious problems.
I know mixing is not money laundering but look at this:
1. Mixer receives money from someone who has done illegal activity.
2. Mixer stores that money on address A
3. I create a mixing order, deposit money to mixer and hours later I declare address B where I want to receive money.
4. Mixer sends me money from address A to address B. Address A has received money from someone who has done illegal activity, so there is a chain: Laundered money -> Address A -> Address B that belongs to me. This is probably what exchanges see and it's very hard to convince them that you are not associated with illegal activities.