"Rotation follows motion path" is greyed out


I want to use Rotation follows motion path but it’s not offered. The manual input of rotations work, but I want the image to flow along the path.

Grateful for any assistance.

The checkbox is only disabled if you have not created a motion path. You can do this if you add a point to an existing linear path, or if you hit the little motion path icon next to the Origin (Left)/(Top) properties: