Connect the keyboard USB cable to a running PC. Test the function of the volume control before putting the roller back to the slot. If the volume control is reversed, no need to rewire the encoder pin connections, just flip the encoder, and insert the roller shaft from the other side.

If the volume control function works properly, then carefully put the assembly back to the roller slot, and similar to de-assemble process. Click in the right side first, and then left side. Make sure the force is applied to the roller bulk shaft not to roller itself when seating the roller.