Vending machines not refreshing

Since a recent update, not sure which one, my vending machines aren’t refreshing (after you click then to collect the coins). It used to only take a couple days for all my machines to refresh, now it’s been over a week and my machines are only half way loaded!. I think the problem is, when I close my lid (on my iPad) and it goes to sleep, the game doesn’t play in the background like it used to. And so nobody is coming to my cafe. I no longer get those pop-ups when I first turn on the game,  “you made so and so many coins while you were away”