Ideas
Recently bought The Sims 4 Love Struck expansion pack. The new world loads correctly in saves created after installing the pack, but in my long-term/older save file the world appears with no visible lots on the map and grey boxes over the apartment blocks.
I can select locations in the Love Struck world for planned dates and events, but I cannot access the world from the map view, move Sims there, or see any lots.
I play on PC. I do not use mods or custom content and never have. I deleted localthumbcache.package and repaired the game. Issue persists only in older saves but works in new saves.
This appears to be a save compatibility issue rather than an installation problem.
I merged your post with the main thread on this.
Please see first post for suggestions.