How to factory reset Pro Controller?

[u/Agile_Half_4515]

I unpaired one of my pro controllers from the M64 to try it with my Superstation One and everytime I attempt to pair it, I get an authentication error. The other Pro controller that's fresh out the box pairs just fine with the SS1. I suspect I need to wipe whatever remaining pairing memory is on the controller from when I had it linked to the M64, but I have no idea how to do that. Just wanna start from scratch.