Here's my suggestion: Post in the TGR910 thread, Yuktsi is responding there.
Before anyone lights me up, the EXENT PCB is the TGR910 PCB. Just the solder mask and silkscreen are different. The EXENT has the same top side RGB mount location the TGR910 does.
I'm on your side about this. Yuktsi told me as much in a PM that the PCBs are identical.
I would also maybe make a separate thread in the workshop/making stuff together or whatever forum, and also try looking through the "PCB design" thread or whatever to see if he can get an idea of what should be working but isn't.
Also PM Yuktsi directly, not that I think that will be terrible useful. He did tell me, though, that if it came to that he would sell me a new PCB. Given the way this project is I wouldn't put too much faith in that prospect though.
I'm sorry dude, as for your PCB picture I can't see anything obvious, aside from some cold solder joins on LEDs. The solder on the switch terminals also look dangerously close to their respective diodes in some places, but if it was working before hand I don't know how likely it is one of these is what's causing problems.
I guess what I would do is seeing if I could backtrace the continuity from the USB plug to...somewhere else on the board. I might also see what signals things are getting on a
functional keyboard and compare those with what's going on with your exent.
I really feel for you, and I wish I could do more. I've gone through this multiple times now where I've had PCB issues and haven't really gotten, I dunno, the
best help from posting online. In every case I've ended up in one way or another finding the fix myself, usually from blind luck.