Mic Monitor not working

My microphone monitor does not work when I click start monitoring ( no lights) and when I push red record button no wavelength shows up, just a flat line.
It was working previously. I did change settings in device toolbar too Windows WASAPI /Lexicon Alpha In/Out (USB) / Mono / Speakers (USB Audio device)
Not sure what settings were before , as soon as I changed from MME, the rest changed.

MME is most compatible. Why did you change host?

What sound are you trying to record? An input connected to the Lexicon? If you are connected only to Line In 2 or only to the mic input, then you must set Audacity to record in stereo to capture that input. After recording, use the Audio Track Dropdown Menu to Split Stereo to Mono then use the X on the silent upper track to close it.