Related Article https://support.microsoft.com/en-us/help/17588/fix-problems-that-block-programs-from-being-installed-or-removed
Follow the steps on the Microsoft article for installing and running the FixIt Troubleshooter program. The FixIt covers Windows 7, 8, 8.1 and 10
Most problems with updating Plex Media Server are caused by corrupt files or missing msi files for the previous version of Plex Media Server. Tools that tidy up the windows environment may remove vital msi files that are needed for updating Plex Media Server. These files would be in C:\ProgramData\Package Cache and C:\Windows\Installer directories. To install a new version of Plex Media Server, it needs the packages for the current version to get that auto uninstalled before the new version gets installed. If these are missing, the install fails.
See this Plex Support Article for further information https://support.plex.tv/articles/202967086-windows-errors-trying-to-upgrade-install-or-uninstall-plex-media-server/
If you encounter errors such as unable to find an msi file, try to Uninstall the current version through the Windows Add or Remove Programs. If that fails with such an error, establish which package it could not find.
The following gives steps of using the FixIt program to help uninstall Plex Media Server.
Use the Troubleshooter initially selecting Uninstalling
Select the Plex Media Server product
On the next screen, selecting Yes, Try uninstall
If this completes successfully, the following is displayed
The following are advanced steps that you may need if the above fails or there is a specific component that is failing
Advanced Steps
If you get errors relating to the msi package for pmsshutdown, then try to use the Troubleshooter FixIt program to remove this component. The name of this product component is Stopping Plex
If this fails, logs would need to be looked into to get additional information for use with the Troubleshooter. There are a number of log files, all with file names ending with .log . They would normally be in %LocalAppData%\Temp and may get auto-copied into the Plex Media Server App Data area within the Installer Logs folder.
Log Files
The Plex Media Server msi log files would have names with the following syntax
Plex Media Server_yyyymmddhhmmss.log
Plex Media Server_ yyyymmddhhmmss _000_pmsshutdown.log
Plex Media Server_ yyyymmddhhmmss _002_pms.log
dd_vcredist_x86_ yyyymmddhhmmss.log
where yyyymmdd and hhmmss give the date and time when the process started
The 000 and 002 may vary
Example of missing msi package cache for the previous version
In this log the update failed because of a missing msi package cache
Extract from one of the msi log files for the update
Action start 08:23:17: RemoveExistingProducts.
MSI (s) (A0:B0) [08:23:17:002]: Resetting cached policy values
******* Product: {9FECFE39-4123-40E7-9BCF-0A0DE93092A7}
MSI (s) (A0:B0) [08:23:17:002]: Warning: Local cached package 'C:\Windows\Installer\5a12ee.msi' is missing.
MSI (s) (A0:B0) [08:23:17:002]: SOURCEMGMT: Looking for sourcelist for product {9FECFE39-4123-40E7-9BCF-0A0DE93092A7}
MSI (s) (A0:B0) [08:23:17:094]: SOURCEMGMT: Now checking product {9FECFE39-4123-40E7-9BCF-0A0DE93092A7}
MSI (s) (A0:B0) [08:23:17:094]: SOURCEMGMT: Attempting to use LastUsedSource from source list.
MSI (s) (A0:B0) [08:23:17:117]: SOURCEMGMT: Trying source C:\ProgramData\Package Cache\{9FECFE39-4123-40E7-9BCF-0A0DE93092A7}v0.9.1204\.
MSI (s) (A0:B0) [08:23:17:118]: Note: 1: 2203 2: C:\ProgramData\Package Cache\{9FECFE39-4123-40E7-9BCF-0A0DE93092A7}v0.9.1204\pms.msi 3: -2147287037
MSI (s) (A0:B0) [08:23:17:118]: SOURCEMGMT: Source is invalid due to missing/inaccessible package.
This example is from a very old failure with a very old version - it just demonstrates the process for getting the details out of the log.
The product code for the version of Plex Media Server that the installer could not remove is
{9FECFE39-4123-40E7-9BCF-0A0DE93092A7}
You can use the troubleshooter FixIt option for entering the package code, selecting Not Listed
And then entering the product code {9FECFE39-4123-40E7-9BCF-0A0DE93092A7} on this screen
Then complete the steps to uninstall it
