I am currently using Commerce module (latest version) on my Drupal 7 website as a web-shop solution.
After installing and configuring all the necessary modules (Commerce, Commerce Shipping, Product, PayPal module etc.), I faced with an issue that the "Checkout" button disappeared after a while (approx. 10 hours) from the Cart menu.
To fix it, I did not have to do anything except clearing the cache, but after ~10 hours the problem came back, and so far it happened several times.
Is there anybody who has any idea what cause this problem and how to solve it?