I have a M5 with same problems - no sound come out, excepts when is used in True By Pass mode, but only when the button ON/OFF is OFF - getting only the original DRY guitar sound bypassed. So, no effects comes out, no wet signal! when the mode is in DSP, nothing comes out.
The pedal is not mine, I got it only for repair. The owner used with an 12V supply and after that attempt, the M5 was damaged.
Also the tuner doesn't work, but I fixed that replacing one of the TL072C opamp from the motherboard.
Seems that internal buffers don;t works - I don't have schematics to be sure where are located. I didn't find the wet signal trace either. otherwise voltages are very clear marked on the PCB, I measured and are fine.
I will apreciate if I get an service manual or some tech advices. I received the pedal yesterday, but now I'm stucked on it.