When customer is upgrading from DLP 15.8 (and possibly other versions) they encounter the error "Cannot access network location DetectionServer\15.8.00000\Protect\Scanners" as per the below screenshot when they attempt to run the msi to install the new version of DLP. This can occur on the detection servers and/or enforce server.
The following errors may also be observed in the msi verbose uninstall log.
MSI (s) (28:54) [07:37:42:821]: Note: 1: 1314 2: DetectionServer\15.8.00000\Protect\Scanners
MSI (s) (28:54) [07:37:42:821]: Note: 1: 1606 2: DetectionServer\15.8.00000\Protect\Scanners
MSI (s) (28:54) [07:37:42:821]: Note: 1: 2205 2: 3: Error
MSI (s) (28:54) [07:37:42:821]: Note: 1: 2228 2: 3: Error 4: SELECT `Message` FROM `Error` WHERE `Error` = 1606
MSI (s) (28:54) [07:37:42:821]: Note: 1: 2205 2: 3: Error
MSI (s) (28:54) [07:37:42:821]: Note: 1: 2228 2: 3: Error 4: SELECT `Message` FROM `Error` WHERE `Error` = 1709
MSI (s) (28:54) [07:37:42:821]: Product: Symantec Data Loss Prevention 15.8.00000 MP3 HF18 Detection Server -- Error 1606. Could not access network location DetectionServer\15.8.00000\Protect\Scanners.
MSI (s) (28:54) [07:37:42:821]: Note: 1: 1606 2: DetectionServer\15.8.00000\Protect\Scanners
MSI (s) (28:54) [07:37:42:821]: Note: 1: 2205 2: 3: Error
MSI (s) (28:54) [07:37:42:821]: Note: 1: 2228 2: 3: Error 4: SELECT `Message` FROM `Error` WHERE `Error` = 1606
Error 1606. Could not access network location DetectionServer\15.8.00000\Protect\Scanners.
MSI (s) (28:54) [07:37:42:821]: Note: 1: 2205 2: 3: Error
MSI (s) (28:54) [07:37:42:821]: Note: 1: 2228 2: 3: Error 4: SELECT `Message` FROM `Error` WHERE `Error` = 1709
MSI (s) (28:54) [07:37:42:821]: Product: Symantec Data Loss Prevention 15.8.00000 MP3 HF18 Detection Server -- Error 1606. Could not access network location DetectionServer\15.8.00000\Protect\Scanners.
It has been determined that this is primarily caused by a missing registry key for the 15.8 install, the exact cause of this is unknown but may be related to a previous rollback of the software after a failed upgrade attempt.
The customer must restore/replace the missing registry below key and then run the msi again.
HKLM\SOFTWARE\Symantec\Data Loss Prevention\Detection Server\15.8.00000\Installation
Manually adding this entry should allow the upgrade to complete successfully.