I wanted to post my situation for future reference.
TL;DR: I installed FreePBX 17, restored from v16 backup which already had my Port Management set correctly, but my FreePBX site was still showing not secure. Simply clicking “Update Now” without making any changes on the Sys Admin > Port Management page fixed it.
I run FreePBX on a Vultr instance, and had been running on version 16 with a Let’s Encrypt certificate. I installed Debian 12 on a new server, installed FreePBX 17, restored my v16 backup, and activated.
I then took a snapshot of the server.
I deleted out my old LE certificate and created a new one after making the proper DNS records changes. Once I did this, I got a message saying that the admin page had been changed to 8080, and every time I went to the site, I would get security errors. I ended up having to go directly to the IP address every time. I looked at the Port Management page and everything was set up correctly. I committed everything, did fwconsole restart, rebooted the server, and nothing worked.
I restored my server from my snapshot to start back from initial install.
Upon setting up the LE certificate again, I had the same problems. While looking at the settings on the Port Management page, which again were just carried over from my backup, I thought I would just hit Update Now to make sure the settings were actually taking effect (I think I had to commit them as well), and I instantly got a secure page (I might have had to refresh the page but I think upon commit it refreshed to the secure page).