More descriptive Verify Product steps

following the steps to verify a product from an external store (in my case: gumroad) it says "verification code not found" For any of my products. If I am inserting the link wrong, I wouldn't know (this is what the instructions told me to do)

If I am doing it correctly and there's something wrong with my gumroad account, could there be a list of reasons as to why the verification code cannot be grabbed?