Hi Mitch,
This is because Rhino 5 didn’t advertise itself as being capable of opening all the file types that it could open. To fix this:
- Unzip rhino5x64.document.reg.zip (581 Bytes)
- Double-click the .reg file to add the registry keys to Rhino
- Now, when you right-click .step, .stl, and all the other types Rhino supports, an option to open with Rhino 5 x64 exists.
Does this help?