Phone not recognizing external 3.5mm microphone topic

I purchased an external 3.5mm microphone about two months ago, and it was working wonderfully (much better audio than internal mic (albeit mono). Two days ago, no microphone input was working (external or internal phone). Today I did a factory reset out of frustration (hey, I need a working mic), and now the phone mic works as normal, but the phone no longer recognizes the 3.5mm mic. When I plug in the Sony noise-cancelling earphones, the audio and speakers work from the earphones, but when I use the 3.5mm mic, the phone doesn't even notice anything is plugged in. Any thoughts/suggestions?

EDIT: I should mention I'm on Lollipop 5.0.2, if it makes any difference. 23.1.A.1.28