Think I just found the reason for this problem, I don't know about forgotten hollow, but I tried this in my 4 towns I'd mentioned, that were missing glass reflection. this fixed my problem:
Just a few weeks ago, I'd turned view distance option in game down to low. (to try to help it run better since it's low end pc). that was the problem for me. I put it back high and now I have reflection outside on windows, doors, roofs. 😞 All that stress just for such a simple fix.
I never would have thought that would have caused it, because, in the past, I used to play alot with view distance low, but I don't ever remember the glass reflection doing that, the only thing that happened when I'd used to put that option down, was if I backed up, the windows would become a solid color that you could not see through like grey or something. *(update: actually I don't think that grey thing happened either with view distance low, I think that specific thing may have happened when I used to use laptop mode long ago. I'm pretty sure low view distance didn't used to do anything to the windows, or I'd have definitely noticed when I played alot back then on low.)*
and, since it was so long since I'd played with that option low, it's impossible for me to tell which patch had caused it to appear as no reflection- missing glass look, with that option down. could have been seasons, and could have been many patches before it.
I'll tag to let you guys know in case it can fix some of yours as well, let me know if it was why you had the problem as well:
@BryonyRae @NeutralSupply @muchlove0007 @CactusFlowerSims @FairyOfLight14 and @LadyDarkSorrow
also letting these guys know it does that on low view distance- @SimGuruIcarus @SimGuruNick It would be nice if it didn't do it on low view distance, because that was one of the few game options that was good to put down to help game not lag so much on low end PC. putting that option down is better than putting sims detail option down and making sims look bad.
also letting @crinrict know, as it may have solved the problem for some.