Thank you!
If you open Task Manager and go to the Processes tab, is dopusrt.exe running there? (Note: dopusrt.exe not dopus.exe)
Are you using anything that changes the Windows desktop at all? e.g. Widget tools, wallpaper tools (other than the built-in Windows wallpaper), Active Desktop type software, or "fences" or similar programs?
Make sure that Opus is not running as admin. If the main Opus process is elevated then then UAC would prevent the double-click message from reaching it. (Using the Admin Mode built into Opus is fine, but dopus.exe itself should not be launched elevated as that makes the entire program elevated instead of just the parts that need to be.)