When attempting to open your project you get: The Document 'yourFileName.cmproj' could not be opened.
*If you are receiving this error instead, "Error: Cannot open project" then please see the following article.
Restore from a backup copy of the project if all else fails:
- Right click (Control + click) on the .cmproj you cannot open
- Choose "Show Package Contents"
- Follow the steps in the following GIF and then go back to the .cmproj and try opening it: