SfB Server 2015 (KB4464355) could not be installed. Error code 1603.

While installing the Skype for Business Server 2015 CU8 on the Edge Server we had the following error:

In the Server.msp-SFBEDGE01-[2019-01-24][10-36-34]_log:

MSI (s) (C0:B4) [10:37:04:023]: Executing op: CustomActionSchedule(Action=CA_InstallDBonPatchInstall,ActionType=3073,Source=BinaryData,Target=ExecuteCommand,CustomActionData=powershell -noprofile -command ” & Install-CsDatabase -Update -DatabaseType Registrar -Verbose “|C:\Windows\system32\\WindowsPowerShell\v1.0\powershell.exe|C:\Windows\system32\)
MSI (s) (C0:B4) [10:37:04:027]: Creating MSIHANDLE (10878) of type 790536 for thread 4788
MSI (s) (C0:20) [10:37:04:027]: Invoking remote custom action. DLL: C:\Windows\Installer\MSI665.tmp, Entrypoint: ExecuteCommand
MSI (s) (C0!24) [10:37:10:516]: Creating MSIHANDLE (10879) of type 790531 for thread 3876

MSI (s) (C0!24) [10:37:10:516]: Product: Skype for Business Server 2015, Edge Server — Error 29024. Error 0x80004005 (Unspecified error) occurred while executing command ‘C:\Windows\system32\\WindowsPowerShell\v1.0\powershell.exe’. For more details, check log file ‘C:\Users\ADMINI~1\AppData\Local\Temp\LCSSetup_Commands.log’.

And in the LCSSetup_Commands.log:

Install-CsDatabase : Command execution failed: The network path was not found.

The issue was the Remote Registry Service was Disabled:

We then temporary configured the service to Manual and Start it:

Back to the Cumulative Update Installer to retry the installation:

The update should complete without issues:

If required we can change back the Remote Registry Service back to Disabled after installing the update: