Currently, MG3 only recognises input from pitches Low E and above — Click on the low E2 on MG3 and it says “Sorry it can’t go any lower … Call back Later”.
If you don’t need to (or are able not to) hear the original guitar sounds then you can tune to drop D (or DADGAD as I do) place a capo on fret 2 and use midi transpose to shift down.
I simply play in DADGAD capo 2 anyway so can use my guitar sound as well or it does interfere with midi sounds.