Belinda, have you figured this out? I have the same issue you are having using Moodle 3.3.5+ (Build: 20180412). We built it on http://, and then migrated to https:// server. Updated the config.php, and our badges are not working for some reason.
As an Admin, I see this warning message on the 'Site badges: Manage badges' page: "Your site is not accessible from the Internet, so any badges issued from this site cannot be verified by external backpack services."
Also, as a Student, I try to send one badge to backpack.OpenBadges.org, and I get this message after attempt:
"You didn't add any open badges to your Backpack. Visit your Backpack to manage and share your open badges."
Then, I try uploading a badge downloaded from Moodle directly into backpack.OpenBadges.org, and I get this error:
"could not get assertion: unreachable"
I see nothing alerting me to issues in my error logs, or when I turn debugger on in Moodle. Very strange.