Well, that's pretty conclusive; the 5V power rail is reaching the display board OK, it is the correct value, and it is at the correct value on the active low Reset pin on the power PIC. However, you measured 2.63 V on the RST pin of the keypad/rotary PIC, which should have been 5V.

Conclusion: you key scanner PIC has passed away, and needs replacing. Good news in a way (you know what it is, and you only need to send the display away for repair), but bad news also (it's f***** and you are going to have to send the display away for repair).

Cheer up, you still will be able to play the music on stream.