Grab a meter and see if battery power is getting onto the board. Could be a bad battery holder.

LTG : )

This is a very easy pinball to just bypass the battery issue altogether and put a NVRAM in.

I buy them here:

https://www.pinitech.com/products/6264_nvram.php

But you may have prior battery acid (alkaline) damage that is just now creeping into the traces that run to the Ram chip.

I'm with LTG, it's easy to test the battery voltage (they give you a VBATT test point!).

But if anything lower than the battery holder has solder connections that look grey, have fuzzy white powder on them, grey green, or discolored (darker) green conformal coating (sometimes in a spatter pattern) you have a board that had previous battery acid (alkaline) problems, and you may need to get your board fixed.

I'd check to see if you are getting voltage from the battery holder, if not, I'd examine the board carefully for battery acid/alkaline, and then just put in a NVRAM if the board isn't compromised.

Good luck!