To reset the sensors,  make sure the full underside of the vacuum, including the black rectangular sections surrounding the bumper edge is cleared off of any dust and debris.

Check that the front of the full bumper is also cleared off.

Then pick up the vacuum and rotate it forward in a full circle, a full 360 around and side to side.
Make sure the bumper itself is not stuck in any section which may be setting off this error.

To do this, check all three sections of the bumper are moving properly.

The front, right, and left section should each be able to press in, and bounce back out into place.