Hitting Ext Source does not work anymore...the light on the button won't come on and not hearing any sound plugging my synth through the mic in. Mic Level all the way up too. I can see the red clipping light activate when I turn up the volume on my synth so I know it's passing through.

Is this a fixable issue at all?

Appreciate any help / advice. Also, new to this site, so let me know if I should be asking this question elsewhere.

Thanks.

I dont know but if you want to sell it hit me up.

I had a pretty similar disaster a while back (can't remember if the buttons stopped lighting up though) and it turned out the ext source RCA's had broke their solders. Took it to a local shop that does repairs on electronics synths etc and they fixed it in a couple of hours, cost me 30 quid.
Fingers crossed its something similarly fixable.