Did you install the socket for the memory. Buzz it out top and bottom. I’m betting you either didn’t get good flow (you should always hit the holes with fresh solder and clean them out again) or killed another thru hole on the memory socket

It’s socketed. Drop the original back in and see if it boots

so.....It worked before you worked on it and now it wont boot. always check your work. Make sure you didn't get a solder bridge under the socket. If need be, you can try removing the socket and hard soldering the nvram in. I would NOT recommend it! Remove the battery holder and get rid of it if your gonna use NVram. BTW, BOP is one if the games that has easter eggs tied to the clock.

https://pinside.com/pinball/forum/topic/repair-log-ij-cpu-d19-d21-locked-on

The other thing to keep in mind is pulling the board in and out can cause a corroded connection to finally break and leave you with a dead board. With corrosion showing on the holder, you could be chasing your tail trying to find a problem that else where on the board.

Oooooo, never a solder sucker on the WPC boards. I actually have a second desolder station with a micro nozzle just for WPC and newer work. I found an Ungar/Weller solder/de-solder station pretty cheap back in the day that I’m keeping limping along. It’s a version of the old hot vac system and does great on the tiny pads and leads for WPC stuff. It’s personal preference. I know some people who tried my setup and scorched the crap out of thru holes. Just gotta keep at it til you figure out what works for you.