Help with a Cart issue on Shopify

I'm looking for help to resolve an issue with my cart on my Shopify store. I recently experienced an error message when attempting to update my cart that said, "There was an error while updating your cart. Please try again." This issue may have occurred after I had made some changes to my website and theme. To be specific, I have installed or updated an app which may have caused the cart issue. I need help resolving this issue ASAP as I have Black Friday promotions going live in less than 24hrs