Server Version#: 1.15.3.876 downgraded from 1.15.4.993
Player Version#: 1.019
after having had the same problem when starting the plex application in my smart hub. I found the solution by going back to the latest version of the plex server that worked correctly.
Unistall the plex server
Re-install the PlexMediaServer-1.15.3.876-ad6e39743-x86.exe
working now
Dont update to 1.15.4.993
