The section on the purchase order that ask for the MM/YY CVC ZIP CODE is the section that is the easiest to add numbers or enter incorrectly therefore not being allowed to finish. If my cc expiration is May 20 2025, then I would first place my cursor on MM/YY and enter 05/25 for May 2025. If you type in 5 instead of 05 and/or type in 2025 instead of 25 the numbers will push into the CVC section and push into the zip code section and it will be an error. This field is very specific and very exact. There is no wiggle room. The CVC is the 3 digit # on the back of your cc. The key here is to take your time, place your cursor on top of each field and be careful to input your information exactly correct.