You are trying to uninstall DLP 15.1 after upgrade, but it returns the following error:
"A newer version of Symantec Data Loss Prevention 15.1 MP1 Detection Server is installed. Uninstallation cannot continue. Please check the Symantec DLP KB for updated information."
The error will also occur for attempted uninstallation of the Enforce Server.
A known issue in the code will not allow uninstalls of 15.1 if more than 2 versions of DLP are present on the system.
Release : 15.1
Component : Default-Sym
It is necessary to remove at least one of the other versions.
For example given above example (DLP 15.1, 15.7 and 15.8 present): you would first uninstall DLP 15.7, then uninstall 15.1.
Before removing 15.1, check to make sure that the highest version is using a different service account for the DLP services. I.e., make sure that it's not using the same account ("protect" or "SymantecDLP") as 15.1 is configured to use.
NOTE: If you uninstall 15.1, and 15.8 is using the same services - the 15.1 Uninstaller will remove the service accounts used by 15.8. After which, they will no longer function (requiring recreation of the services, or a reinstall of DLP.)
Tested steps for Enforce Server - for a Detection Server with this issue, substitute appropriate keynames, e.g., "Detection Server" for "Enforce Server".
Steps for removal of DLP 15.1 in Windows, to prevent the uninstall of 15.1 from also removing the "SymantecDLP" service account from higher releases.
[HKEY_LOCAL_MACHINE\SOFTWARE\Symantec\Data Loss Prevention\]
[HKEY_LOCAL_MACHINE\SOFTWARE\Symantec\Data Loss Prevention\Enforce Server\15.1]
[HKEY_LOCAL_MACHINE\SOFTWARE\Symantec\Data Loss Prevention\Users\<SymantecDLP>\Versions\126.96.36.19923]
[HKEY_LOCAL_MACHINE\SOFTWARE\Symantec\Data Loss Prevention\Users\<SymantecDLPUpdate>] - note that removal of this key should remove the next 2 subkeys as well.
[HKEY_LOCAL_MACHINE\SOFTWARE\Symantec\Data Loss Prevention\Users\<SymantecDLPUpdate>\Versions]
[HKEY_LOCAL_MACHINE\SOFTWARE\Symantec\Data Loss Prevention\Users\<SymantecDLPUpdate>\Versions\188.8.131.5223]
If this issue occurs with only 2 versions of DLP present, please check the following article for a different issue: