Update File and Retain Customer Access?

Hello, I’m starting a business that will sell digital files and will rely on regular updates to those files. I need my customers to be able to access their previous purchases on their account and download the new files whenever I update them.

Currently, everything seems to work except when they download the zip file and try to open it, it’s a corrupted file.

The page I need help with: [log in to see the link]