The time reset is likely what caused the problem. As stated near the top of
this post, changing the clock on your device can be harmful to both the app & the device itself.
There are a couple of ways to resolve the problem: If you are still in the first generation and want to "start over", you can evict your family without affecting in-app purchases and game progress. That may force your Flea Market to restock, although it is not guaranteed. Otherwise, you will need to wait until the time issue resolves itself. Pausing the game may ease the wait time.
Please note that if you have purchased any coins, you should definitely
not delete and reinstall the game in an attempt to resolve a problem with the game. Doing so will cause you to lose all of your purchased coins, and we have no method of restoring those purchases, due to how Apple's In-App purchase system operates.