MarketPress Shopping Cart no longer adding regular products after Appointments + installed

Now that I have Appointments + installed and integrated with Marketpress, the products that are not related to A+ are no longer showing up in the shopping cart.

The user can click on the add to cart button for any item, and it will generate an item added message, but when refreshing the shopping cart, the item will not be there.

The A+ items DO show up in the shopping cart though.

What do I need to do to fix this?

Thanks for any help!