I recently bought a 2001 S80 that only had 57k miles on it. So, obviously, this thing sat for quite a long while somewhere, but it feels and runs great. However, when I connected my OBD Fusion to it, the "Monitor Tests" screen shows "unavailable" for every test result except for "Components", as in this screenshot.



I've owned other Volvos of this vintage, and they've all shown other tests in this screen as available - most of them, in fact.
Questions:
1 - Could this have been caused by some long period of time with dead or disconnected battery?
2 - Is there anyway for a DIY guy to fix this, or will it fix itself?
3 - If I don't bother fixing, am I likely to never see any "check engine" lights caused by oxygen sensors and the like?

Thanks for reading.