Hi Belinda!
I would like to help for stopping your frustration
I wasn't able to reproduce this using Moodle 3.4 and HTTPS so I guess you've some issue with your site configuration.
- Is your site public, i.e. it can be accessed from anywhere?
- Have you tried to access from your Moodle site to other HTTPS services, such as any external tool activity (LTI)?
- If you enable debugging, does any message appear?
- Have you ever look the response from you server using the Network option in Firefox or Chrome? It's not easy, but if you could try it, probably we'll get the exact error message with the main reason for not being working the connection to the backpack. For instance, if your Moodle site URL is not public (so it can't be accessed from outside), you will get the following error: "could not get assertion: unreachable"
Kind regards.