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.
You said you have not done it in any other platform, then you would have narrate everything happened so people would have called the attention of Yo!Mix here to verify but here, it is an allegation without prove that Yo!Mix was the one. That screenshot might be a transaction you had done at somewhere else.
Yomix not owe anything to respond to this particular topic, it's a matter between him with Uphold.
@OP should change the title to "Warning, Uphold is refuse funds from mixer".