Mitsubishi Servo System encoder error [A16]

I'm a garage tinkerer and I'm trying to use a Mitsubishi Servo System to turn the chuck on a lathe. The Mitsubishi servo drive displays an A16 error as soon as it's powered on. That's an encoder error, but I've double-checked the cable between the encoder and the drive and I've tried two different encoders. Still just "A16".

Is it necessary to provide some kind of reset to the driver to clear the error?

I don't have an oscilloscope, but tried connecting a meter to one of the encoder signals (with a 5V power supply providing power to the encoder) and the voltage doesn't vary as the encoder shaft is turned.

Any suggestions would be greatly appreciated!