According to official support channels on the Boris FX forum, the "Matte Assist ML Render Failure" almost always points to an issue with your computer's hardware, specifically your graphics card (GPU). Here are the primary causes:
Do not render Matte Assist at full resolution immediately. In the Matte Assist module properties, set "Render Resolution" from Full to Half or Quarter . Once verified, you can render the matte at full resolution using Mocha’s "Export Matte" feature separately. matte assist ml render failure mocha pro verified
Render Failure when using Matte Assist ML in Mocha Pro (Verified Issue) According to official support channels on the Boris