I've searched the forum and the last update I found was from 7 years ago. Reposting as this is a new issue for me.
Product: Sims 4 Platform: PC Which language are you playing the game in? English...
Ideas
I am posting this as it appears some of the posters on this thread might not understand how the collectables spawning works and may think their game might not be working correctly.
Dig rocks, dig spots, frogs and harvestable plants act differently in different worlds. In most of them, once you collect them, they will respawn in about 24 hours when you stay in the zone. If you just go collect them and leave the zone, they won't be there when you return as the spawning timer only works while you are active in the zone. So, to get them a second time, you have to stay in the zone for the entire 24 hours. Each item has a different spawning interval as well. If you have Seasons, that changed the plants, so they don't have a timer like they do without Seasons, and only spawn fruit between 5 AM and 5:30 AM every day. There are no worlds where the plants spawn their fruit on lot load other than the first time you visit some of them in a new game. That varies on the world. Some do, some don't.
There are several places where the collectibles other than plants, work differently. In Brichester, Tomarang, and Granite Falls, the dig rocks/spots only spawn on lot load. In Tomarang, the frogs do too. Once you have collected them all, they will not respawn again for as long as you stay in the zone, even if you stay there for days. But, if you leave and return immediately, they spawn again. So, you can exploit this by collecting everything in a zone, go to another zone in those worlds, collect everything, go back to the first zone, collect them again. Rinse and repeat as many times as you want to.
SelestialFox On the science lab. It's not the one in Strangerville. It's the one from GTW that you can only access by having a sim in the Scientist career. The plants there can only be harvested once since they are also on the 5 AM/5:30 AM harvest cycle if you have Seasons. The rocks will respawn daily though so if you collect them on one workday, you can do it again the next.
Keep this in mine. For most zones, whenever you leave a zone, the spawn timers for everything but plants stop and does not restart until you are back in the zone. You get nothing if you don't stay there continuously for 24 hours after you collected last. For plants, you must be in the zone prior to 5AM if you want to collect the fruit they bear.
Hope this helps.