Structural Synchronizer is installed and the Synchronizer Viewer can be used to view an existing repository, but using Create Repository or New from Repository from any ISM enabled application produces an error such as the one below from Ram Manager (Version 15.08):
Background ISM error ("Could not create ISM interface 5.0") at Bentley.IsmRssLink.BackgroundIsmStartup.CheckErrorMessage()
With Revit 2017 the error is something similar, but referencing “ISM interface 6.0”
The problem occurs because one of the .dll files installed with Structural Synchronizer Update 2 was not properly "signed" and hence does not get installed correctly on some machines.
Install version 10.03.00.08 (released October 2018) or later.
Error - Could not start a responsive EngineRAM Manager Crashes when using ISM - New From Repository