This problem happens with specific projects. When attempts to export from CA PPM to MSP the project appear blank. This happen with new and legacy driver.
This could be for several reasons, one of this is that the project was imported from a Microsoft Project Server, which is currently not supported, this kind of projects export external attributes that blocks the project when try to export it from PPM to MSP.
Delete prdocument register in order to remove external attributes generate by project server.
If you are OD customer, create a case with support in order to execute the query.