This happened due to a partial installation which resulted in smaller than expected file sizes in the bin directory under C:\Program Files\Symantec\Workspace Streaming (default directory). In a normal case, if the service is not running the uninstallation will start the service and complete the operation. Because the files in the bin directory were not complete files, the service did not start and the uninstallation failed.
Error message indicating uninstallation failed because the streaming agent service was not running.
On a known working machine, copy the contents of C:\Program Files\Symantec\Workspace Streaming\Bin and place them in the same directory on the problem machine.
Perform the uninstallation
Install the newer version
Symantec Workspace Streaming (SWS) 7.5