Digital download failed or zip file cannot be opened

You may find that downloading individual images works fine but downloading of an entire gallery fails — sometimes with a zip file that cannot be opened. The Digital Downloads add-on builds zip files of all the images in the gallery on the fly to save server space on your web hosting and also build a zip file of only the files the specific user needs. However, this process can be server intensive and cause the process to fail if the server cannot handle the load. This will all depend on the resources of your web server, the size, and quantity of images being put into the zip file. Also, if you are on a shared server, the available resources may fluctuate throughout the day based on how busy the other sites on your same server are.

Increasing Memory

The most common fix is to increase the available memory for your WordPress installation. This solves the issue for most cases.

Background Download Processing

If you're still running into issues, large downloads can optionally be processed in the background instead of streaming in a single request. As of Digital Downloads 3.2, any download over a file count you set is queued automatically. The customer sees an instant confirmation, then receives an email with a secure download link when the zip file is ready. This is especially helpful on shared hosting or servers with limited resources.

For setup steps and a full walkthrough of how the queue works, see Background Download Queue.