File is "not a Rhino m_archive"

Rhino Rhino for Mac
1

Trying to open a file in Rhino6, and it will not load…error:

Users/JM/Documents/Jenny/TEACHING/F19_CPP/2500A/Tutorial.3dm is not a Rhino m_archive.

2

Hello - please send the file to tech@mcneel.com. Please include a link back here in
your comments.

-Pascal