Currently, the Mocha Pro 2019 OFX plug-in does not officially support Resolve. Blackmagic is aware of the support issues and has committed to working with Boris FX to make this work in the future.
Currently, Mocha Pro standalone software can run on a Resolve system and can be used to render object removes, stabilization, screen inserts and mattes to be imported into Resolve.
Additionally, both Continuum and Sapphire OFX plug-ins do support Resolve and include a light version of Mocha for tracked masks and effect isolation.
The Fusion 9 standalone application does support Mocha Pro 2019 OFX plug-in, however the Fusion panel inside of Resolve 15 does not.
Please view the Mocha Pro 2019 tech/specs chart to see more.