You should never go out on the web and download any old dll file from “somewhere”.
That’s just asking for malfunctions or, worse, infection by a virus.
Download the Plex server installer again from below.
Afterwards, verify it’s cryptographic signature for validity.
If it’s not valid, download it again, this time by using a different web browser or a download manager software.
Then
Stop/quit/end Plex Server with the tray icon
deinstall Plex Server with the regular ‘Apps’ control panel of Windows (do not use 3rd party ‘Uninstaller’ software like Revo etc.)
for safety, reboot Windows
start the installation exe of the newer PMS version
After the installation, inspect the event log of your anti virus software, just in case it decided to remove some of the freshly installed files…
Thanks for you answer, I downloaded PMS from plex.tv
but nothing new after new installation
no virus detected !
reboot windows
now error : (0xC000007b)