There is not a lot that can go wrong here, either you are missing battery voltage to pins 20 and/or 28 of the RAM, or you have a bad RAM. The voltages are very easy to check and I suspect if they are missing that at some point in this games past the batteries may have leaked and eroded the board connections at either the battery holder or at D201.
Since this is a Whitestar game with socketed RAM at U212 the easiest solution is to drop in NVRAM and get rid of the batteries.
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