Slow Clip Problem in Pr

Whenever I use a slow clip in premiere to use in mocha, and enable matte, it never works.

Can you clarify what you mean by “slow clip” ?

What exactly are you trying to do? Can you show an example?

Do you mean you are applying Mocha to a time-warped clip in Premiere?
You may want to “nest” the clip before applying the Mocha plugin in Premiere.