The topic was definitely private at the time of mailout, as you can see the ‘Private:’ just before the subject.
If you hover over the topic link, you’ll see it’s a huge URL, containing
bbpnns-digest-login=1. That’s the part that makes you log into the site in order to see the topic.
However, the functions I call to build the link,
get_permalink() are returning the httpS link, instead of http. Your Settings > General seems to be using
WP_SITEURL pointing to the non-SSL version of the site.
I don’t know how it is that you set it up initially that would return the httpS link. You probably have it set that way in the database.
So, first things first – you should get your SSL fixed, as it’s Google’s new recommendation. Depending on your host, you can get a Let’s Encrypt free certificate with a click of a button. I do that for all my sites and clients who host at Siteground (yes, it’s an affiliate link, but I stand by them).
Second, I’d try to figure out why those functions are returning https.
Third, I’d try to figure out why your WP is not showing the available update for the Digests plugin. I definitely see the check hitting my update server, but your install doesn’t seem to be accepting it. I know it’s not the updater class bundled with the plugin because I got the update notification on all my own installs.
And finally, something seems to be interfering with my login redirect code. After you’re presented with the login form, it’s supposed to take you to the post you clicked on. However, there seems to be a higher priority login action that’s taking precedence. I’ll release an update with a fix for that, but then we go right back to the third item above.
I hope this helps!