First make sure there is nothing to collect in the areas I have highlighted in the pic below
It is known, or at least was before the Update 101 that the checkmark was still thee even if everything was collected
in that case, contact support
This forum is provided by EA but is designed as Player helping Player, in this case we can not do much for you
Contact support: Get there in game: green ... button at the bottom of the screen; info > online support
Or use the web https://help.ea.com/en/help-top-issues/?product=the-sims-freeplay
Or contact support via FB or Twitter, links are at the bottom of the page
