Trying to move joint 0

Hi all, I'm trying to move joint idx 0, the base of the neck, by sending "m0 x" where x is an integer that oscillates between -30 and 30. The joint doesn't move, but when I switch it to "m1 x" the head nods as expected. Am I using the command right, or is there a bug I need to figure out? I've verified that the servo still works by testing it externally, and I've double checked that it's wired to pwm pin 7