OBD missing data on my S80
 

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.
https://cimg0.ibsrv.net/gimg/volvofo...0aefdf01dc.png


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.