The error during installation was:
Service 'FileOpen Manager Service' (FileOpenManagerService) could not be installed. Verify that you have sufficient privileges to install system services.
Support at FileOpen responded very quickly with the following:
Please run this program: http://plugin.fileopen.com/tools/FileOpenUninstallTool.exe
Then install via this program: http://plugin.fileopen.com/new/current/FileOpenInstaller.exe
This resolved the problem and FileOpen installed with no issues.