Happening to me too. I'm thinking it may have something to do with the transition to the new button system (which is pretty ugly imo). Our only options are the button set (paypal, venmo, paylater, debit) and a payment link, none of which offer an add to cart function. I haven't actually attempted to buy something from myself, but I'm pretty sure it just sends you immediately to checkout, requiring customers to purchase items one at a time with no combined (a big no-no for businesses). My current add to cart buttons are all broken too, but they seem to be "flickering" where they work one day and don't work another day.
It's too bad we couldn't just create an item for sale on the current system and copy the ID and paste it into existing add to cart buttons, but seems like the actual functionality of the cart is being phased out outright 😞
