@jester 1.21 RC2 and above should support the P9 probe type. 1.21 is quite old at this point though. I'd suggest looking into updating to 2.02.
https://duet3d.dozuki.com/Wiki/Installing_and_Updating_Firmware
Can you post your homing files as well? Do you happen to have an M558 command in them?
What happens if you send your complete M558 command in the gcode console and then send M558 again with no parameters. Does it read back type 0, or type 9?