[GALLERY] 'Content not installed' warning with all content owned

Thanks! I actually came to delete my post because after ENDLESS troubleshooting I finally figured out my issue was the dreaded blacked out photos. I don't normally use photos at all so I didn't think to look for it. 

After I fixed the issue on ONE lot the other one still wasn't working so I didn't think the photo issue could be the problem. Then I just happened to spot a random black photo all the way at the bottom of the wall, mostly hidden under a doorframe. Once I deleted that, the lot uploaded and downloaded just fine! 🤦‍♀️ (So no more "System Error" messages.)

FYI -- I am still getting the "Content not Installed" message every time I download an original build from my library, despite the game recognizing that I do own everything in the lot (or sim, it's happening with sims too...). 

And it's happening despite the fact that I just this week uninstalled and re-installed the full game, and confirmed that every pack I own is in fact activated. And the lots & sims it's happening to were all built by my from scratch without CC or mods. 

Oddly enough, the remodels of original Maxis-made lots are uploading and downloading into my library just fine, despite the fact that I am adding loads of new items to them from all of my owned packs. Why it only happens to original build & sims is beyond me.