After some conversations with Gil (from Ortur) it turns out that their firmware people added some “features” to one of the settings in the machine.
Short version, $22=0 to turn off homing, $22=43 to turn it back on (ONLY for the Ortur).
Longer version: In GRBL, the homing enable setting ($22) is a boolean, meaning it can be set to 0 (off) or 1 (on). They turned it into a bit-field, meaning it now has other features, so “on” is now 43.
bit0 : 1 (homing enabled)
bit1 : 2 (??)
bit3 : 8 (??)
bit5 : 32 (??)
----------
43
Why they did this is beyond me. I think they were trying to get clever and not have to add another setting, forgetting that this will break every GUI that exists and knows that this setting is only supposed to allow 0 and 1.
They are apparently going to fix this in an upcoming firmware update.
Using $RST=* will also work, because it resets all settings back to their factory defaults, but using the $22=43 setting means you won’t lose any changes you made to things like acceleration, speed, etc.