Sweet Tooth Town won't upgrade

When you get to the "Out of Stock" in a store, you're supposed to be able to upgrade the store if you have the coins. I have the coins, but my upgrade button is grayed out and won't let me update a couple of the stores where I've reached the required level to do so.

Yes, cache gets cleared every day, as well as the restart & other things usually suggested. This has been going on for over six months, but I have not brought the issue up because it seems like issues are never resolved (still waiting on Daily Sudoku to be fixed).