I'm glad you solved it.
For the benefit of anyone else reading this, after homing the arms, you must move the arms to a position that is away from the extremes and within the printing area that you declared using M208. The usual way of doing this is to use a G1 H2 move to move both arms. The example homing files at https://duet3d.dozuki.com/Wiki/ConfiguringRepRapFirmwareSCARAPrinter#Section_Homing_files do this. However, I think a regular G0 move ought to work too.
