How do I fix my Shopify cart page when clicking “Checkout” just redirects back to the cart?

This loop occurs when your Shopify cart’s checkout form action is missing the correct /cart form target attributes, or when your background inventory checker finds products in the cart are out of stock.

“I’ve seen this dozens of times, it’s typically a checkout form pointing to the wrong target, or your inventory checker quietly flagging something as out of stock. I’ll find the loop and break it within 24 hours for $99.”
— Jeff Bollettino, Managing Director, Ignite Conversions