If you are trying to run a live motion control move and get a pre-roll failure message, it means that the rig could not back up into the required position.

If your programmed move has any velocity at the beginning, the motion control rig must back up sufficiently to be able to reach that velocity at the moment it hits frame 1.

So, if you start a move at an axis limit, and it has velocity immediately (frame 1 and frame 2 have different positions), you will get a pre-roll failure.

You can solve this by not starting moves at your limits, or having at least one frame before starting movement.