Talon SRX PWM Calibration Failing

For an off-season event, we are making a minibot that will use an Arduino UNO controlling motors through a Talon SRX. The Arduino receives a signal from a controller and then sends a varying PWM signal to the Talon SRX. When we try to calibrate the Talon it fails the calibration. We have tested the PWM signals that the Arduino is sending and verified that they are correct. Any ideas as to why this might be happening?