Failed: Network Error occurs when a customer attempts to download a file.
The issue is often caused by the EDD store’s server terminating the connection early. This could be because the file is too large. Otherwise, due to the fact PHP is running a thread/process required to deliver the file to your customer. We recommend reaching out to your host to review the server logs and increase the the timeout/expiration on your server, allowing the customer to download the file without it timing out.
Another cause could be caching. Gzip compression could cause this but as a troubleshooting step, all cache should be temporally disabled to see if that resolves the error.
Depending on the quality and limitations of your web host, a more stable long term solution would be hosting your files on Amazon S3, Dropbox or GitHub. This would address most download issues you face as the files will be served directly from Amazon, rather than your server.