Ramps change & D8 pin not working, maybe Arduino mega broken? (1 reply)

I had a ramps 1.3. (Marlin 2.0, Prusa i3 clone).
D10 was faulty so instead of using D10 & D8 i changed in pin_RAMPS.h in D9 and D8.
Extruder and bed worked just fine.
Some days ago I bought a Full Graphic Smart Controller (to use SD and not be in connection with the computer).
The SD didn't work.
So after several attempts I installed a new ramps 1.4.
SD is now working, reading gcodes in it.
Extruder mounted on D10 still not working. So I realized that the issue was not on the RAMPS but I think it's the Mega board.
Switched back to D9 and working.
The problem now is that D8 (the bed) is not working (while instead it was in RAMPS1.3.
The D9 (extruder) has 12V and the red led on the ramps is on.
D8 no voltage and led off.
If I put the bed on D9 (just to test), it heats and works.

SO:

1) can the D8 pin on the Mega board be gone?
2) is there any software that quickly run a diagnostics and says which (and if) pin is gone?
3) any suggestion to fix (D10 as mentioned was not working) or shall I buy a new mega?

THANKSSSSSS