.stl file keeps opening in Rhino 5 instead of 6

I have set the default program to open .stl files to Rhino 6 and no matter how I try it opens in Rhino 5. Unless I open 6 first and import. I would like to double click a .stl file and open in 6. They were converted to .stl from a Rhino 6 3dm file

Same problem here.

The main thing seems to be the way file type associations are handeled in Windows. Say you associate .stl files to Rhino, Windows will look up the Rhino Application in the registry. It finds an entry called Rhino.exe and launches the file at the location
If you had Rhino5 installed, this will very likely point to the rhino 5 program path.
Looks like this isn’t updated even after you deliberately select the app to open with as Rhino 6

My solution was to edit the path in the registry.

Maybe you could just rename the rhino 5 version to rhino5.exe. Don’t know if any plugin or Rhino itself will break as something expects the executable to be called rhino.exe.

Thank you , I’m not sure I want to risk breaking other parts of Rhino 5 since I still need it for T-Splines