Why isn’t mmMidi responding to any input?

Firstly check you are using the correct DIN to TRS adapter cable as supplied with the module (It should be a Type B cable!) . This is very likely the issue!

To check mmMidi is responding to any MIDI, hold the mmMidi’s learn button for approximately 1 second to enter learn mode (indicated by a flashing red LED) then send a MIDI note (i.e. by pressing a key on your connected midi keyboard). The LED should begin flashing faster.If there is no response and the LED speed does not change it's likely you are either using the wrong/faulty adapter (most likely!), your MIDI cable is faulty, or your MIDI keyboard is not connected/set up correctly.