At which point did it give 7 flashes? Did you have everything connected when you had 7 flashes? I would try to connect the strict minimum to the board. The next flash you are missing is related to the PIA and it always possible that something is shorted on the playfield and it is not allowing the PIA to act properly during boot. You have a new board and are repairing that machine which means, it has issues before I assume. Did you verify the dipswitches and made sure they are properly set for Mr Pac man? No switches have been slightly nudge when manipulating the board and are maybe in between 2 sides?

Right now your board stops when trying to test u10. U11 is the exact same chip and can be interchanged, but if a connection damaged or is preventing u10 from working properly, unless identified it would cause the exact same issue. You have to eliminate all possible causes one a time, so start with the bare minimum to boot the board, add another connector and boot again and so on.