Plex home member's server won't allow direct remote access connections

Server Version#:1.43.1.10576
Player Version#:1.112.0.359-0d79a49f
My sister has a home server that is shared with me - I have a Plex Pass, and she is part of my Plex Home - not sure if that counts as her being allowed to use remote access in general under the new requirements and I would like an answer on that, but it shouldn’t matter here, because my account does have the pass.

Late last year, remote access to her server broke. At the time it wasn’t critical, and we didn’t mess with it much. It was prior to her upgrading to the new version that had to be manually updated recently, can’t remember the versions. In any case, I think she wasn’t logged into plex on the server for a while, and we blamed it on that. But she updated a few weeks ago, and remote access is still broken; ran additional updates to be at the latest as of this week.

We have tried a bunch of different things, including everything relevant at the “troubleshoot remote access” support page, but remote access continues to show “not available outside of your network”.

Her ISP is Xfinity, and using the provided modem. A few years ago and up until late last year, remote access just worked, presumably through UPNP. Since it stopped working, we set port 32400 to be forwarded to the computer hosting the plex server with a manual rule, just in case UPNP wasn’t working. I have tried both manually specifying port 32400, or unchecking manually specify port, it shouldn’t matter either way but it doesn’t work either way. We also tried forwarding to a different port, but it didn’t help and we turned those settings back off and went back to 32400. The computer is on a static IP, and the port is forwarded from external to internal. There is no way to do split forwarding (different external port than internal) on the xfinity router, so that is why we went back to 32400.

I have seen reports that xfinity advanced security can cause problems with port forwarding, so that was enabled initially and is now disabled. At various points, I have gotten different responses from port checker as to whether port 32400 is open - at no point have I actually seen Remote access be reported to work, regardless of response there.

I can access the server indirectly, but only some of the time. Other times it just spins. My server works fine with direct access, but I have a different link and ISP and server host (linux), so very little in common here.

Secure connections are preferred, but not required. Everything works fine inside of the home network.

I have reviewed the long post from last november where many people have indicated loss of remote access with a stuck certificate; a few other posts seem to have the same issue. I don’t know if that is an issue that can impact Windows servers or if it is only on other platforms. I don’t see any way to check for myself.

Anyone able to give me additional advice here? I’ve been using plex for 10+ years, have a lot of networking experience, and this has me quite stuck.

Happy to share logs and my sister’s username in a DM to anyone from Plex who can help, prefer not to post it in the open here - I’ve looked in the logs and they have your Plex email address all through different files.