Download doesn’t start. No errors?

I installed the plugin and set up a test piece of content (a PDF) for download. Everything seemed to go smoothly. The shortcode worked and I saw the “enter email to download” option on the web page. I entered an email address and received an email with the download link.

The link appeared to be correctly formatted:
https://mywebsite.com/?file=mydownloadablefile.pdf#038;nonce=5a0e239c45cd10f7ee71f8502c141651&[email protected]

I clicked the link, the homepage loaded…and absolutely nothing happened. No download starts.

I’m running the latest WordPress. I tried disabling all plugins and turning on WP Debug, but it made no difference. There are no errors that I can see and clearly it’s not a plugin conflict. I’m using a pagebuilder plugin (Seedprod), but when I disabled all plugins the site reverted to the Twenty Twenty Two template, so it’s not a template issue.

The only thing I see in the inspect console is a warning about mixed content:

Mixed Content: The page at ‘https://mywebsite.com/?file=mydownloadablefile.pdf#038;nonce=5a0e239c45cd10f7ee71f8502c141651&[email protected]’ was loaded over HTTPS, but requested an insecure element ‘http://mywebsite.com/wp-content/uploads/2022/08/cropentropycstinysrgbfitmaxfmjpgixidMnw1Mzc1fDB8MXxzZWFyY2h8MzF8fGFmcmljYW4lMjBjaGlsZHJlbnxlbnwwfHx8fDE2NjE3NDI5OTYixlibrb-1.2.1q80w1080type.jpg’. This request was automatically upgraded to HTTPS, For more information see https://blog.chromium.org/2019/10/no-more-mixed-messages-about-https.html

Any ideas?