Most likely broken. If you open it you’ll see that the module is very small, and weak. It is just soldered on, no sort of reinforcement at all. Open it up and closely inspect the module, use a digital microscope if you have one. It could be anything from:

1) The plastic shoulder button broke on the inside, disassemble remove the plastic R button, press the module button with your finger and see if it works, if it does work replace the plastic R button.

2) The button module broke off of it’s solder joints, resolder.

3) The button module tabs broke, solder in new module.

4) PCB broke at the button module location, toast, get new pcb or new joycon.

Good luck.