If your DI input is working, but your mic input isn't, there is almost certainly an error with you DI relay circuit. If the circuit is not working correctly, it will be stuck in DI input mode.
Confirm all 8 leads on relay K4 are soldered. You should also check the values and soldering on R19, R20, and Q1.
When you power the unit you should hear a little "click". That is the input select relay flipping to mic input.