Plex will display a „green“ remote access indicator while testing connectivity and only switch to „red“ once it’s confirmed not to work. In such a case it’s fair to assume your remote access isn’t working in the first place.
Did you already verify if the forwarded port is still visible outside your home network (e.g. no newly introduced blocking on the end of your ISP)?
I have read all the support articles from Plex, I have no idea what they are talking about or what a forwarded port is. I just know Remote used to work (on and off) and now it works 0% of the time.
Any guidance on what I should do would be helpful.
Requests/connections from outside your home network cannot simply access devices/systems/applications in your home network.
There’s mechanisms how an app can publish itself, if supported/allowed by the router (UPnP). Another option is to establish a „port forward“ in the router. This means the router will pass outside requests to a specific port to a defined system inside your home network, where the request will be handled (here: your Plex Media Server).
According to the screenshot in your first post, you seem to have had a working port forward at some point (telling Plex to use port 32401 for any of its apps when trying to talk to the server remotely).
You should be able to verify if that’s still active in your router settings.
Beyond that, you can use a service like canyouseeme.org to test if the defined public port is accessible (or blocked) from outside your home network. As a bonus you can double check if the public IP recognized by canyouseeme.org matches that listed on the Plex remote access settings (90.190.xxx.xxx).