My Plex Server suddenly says I am not authorized

Server Version#:
Player Version#: Version 4.156.0
<If providing server logs please do NOT turn on verbose logging, only debug logging should be enabled>

I get the message: You do not have access to this server. Why Not?

I followed the steps regarding removing the registry entries, then logged back in but still the same error.

Can you post a copy of your server logs ?

How can I get the server log if I cannot access the server?

In Windows, open File Explorer. Paste the following path into its address bar:
%LOCALAPPDATA%\Plex Media Server

Within that path, you should find a Logs directory. Right-click it and select Send to -> Compressed (zipped) folder. This will create a ZIP file named Logs.zip.

(This assumes you are using the default location for the Plex data folder.)