It worked fine before they forced me to change my password
Changing the password in the manner they suggested signs out all devices, including your server. So it must be claimed again. I’m not sure what you did before posting in the forum, so I’m suggesting some known best practices. If they down work, I’m not sure why.
I do not know what claiming a server means, or how to accomplish it. I just want to stream the music files on my computer to my stereo, like I used to be able to.
Now the “Your Media” at the bottom of the list is gone again
Make sure your browser is NOT trying to sign you in with your OLD credentials.
When you open Plex/Web it should ask you to sign in, if not, then go to the Plex user icon (top right of screen) and click on Sign Out. Then click to sign back in. Use your NEW credentials to sign in, the browser should now ask if you wish to update the username/password, make sure you click on Yes/OK.
Then click on the Spanner/Wrench icon (top right of screen) and go to General (NOT Plex Web > General).
Beside your user icon you should see your email address and it should say the server is claimed.
If not, then click on the Claim server button.
Then open the Plex/Web Home page, click on the More > button (fly out menu bottom left of screen) and pin your libraries to the Home page once more.
Fingers crossed you should now be back to where you were.
I’m not sure which of these issues or fixes applies to my situation.
I am in my account, but after enabling 2fa, I’m having a problem that I had previously when I migrated from one synology to another. The old server moved but shows separately, and then I pinned the folders. I can’t claim it because it’s not the main one.
Attached is the original response, but there is no “cert” file to delete with the latest updates.
It is not using the old credentials. I created a totally new email to use, and it shows a different user name.
I just signed out and signed back in. It does not ask me to update anything.
When I click on the wrench thing, it takes me to Plex Web - General. There is no other option. I do not see any way to just go to General.
Open Plex/Web and go to Settings > Authorised Devices > Server and remove all instances of your server, except for the most recent instance.
Close and reopen your browser, you should now see only the current server in Plex/Web.
Go to Plex Settings > Server > General and make sure the server is claimed.
Open Plex/Web and go to Settings > Authorised Devices > Server and remove all instances of your server.
Close and reopen your browser and type in http://127.0.0.1:32400, you should be asked to sign into your Plex account/server.
Go to Plex Settings > Server > General and make sure the server is claimed.
Something worked. I’m not sure what exactly, but I now had a button to claim the server.
Thanks for responding so quickly.
You are most welcome.
Happy Plexing 
There are no instances of a server. It only lists Chrome three times. When I try to close those, it signs me out, then once I’m signed back in the three instances of Chrome are back.
When I close and reopen the browser, then put in that address, it takes me back to the Plex home page, no signing in required.
How do I find “Plex Settings”?
Click on ALL (center of screen) and then select Server.
Your browser is now automatically signing you in.
Spanner/Wrench icon on the Plex/Web Home page (top right of screen).
On the “authorized devices” page, the dropdown has three options: All, Other, and Web. There is no option for Server
Under “all” there is no server listed. Just the three instances of Chrome I already mentioned. I see that one says below it Plex Mediaverse Windows, and the other two say Plex Web Windows.
Do you have the Plex server running in Windows? You should see the Plex icon in the system tray (bottom right of your Windows screen).
I do not know what that means. I have uninstalled and reinstalled the Plex Media Server dozens of times tonight.
Thank you very much. This solved my problem.
No, I have nothing that looks like that on my computer.
