This one was probably one of the quickest fixes I've done. I ordered a Nintendo Popeye board as I saw it rather cheap. I got it, hooked it up, and got no boot.

First thing I do in games that don't boot like this is reseat all the chips and swap the CPU (if I can easily do that) with a known good one. In this case, I only reseated the ROM chips on the CPU board and replaced the Z80 with one of my new old stock ones I bought recently. After doing such, it booted right up!

Turns out the Z80 itself was bad, luckily I have several on hand, so it was a quick fix.