Mac and No Default Clip
This applies to all Mac versions post Mac Sierra, and all MXWendler versions
In Live Editor, trying to insert a clip by clicking on New Clip insert an empty clip with no video.
Under new versions of OSX, Gatekeeper dislocates unsigned applications to random paths on start resulting some of the software paths to not work.
You need to disable the App Translocation function of MacOS Gatekeeper. Please follow this troubleshooting: Mac Sierra 10.12 Disable App Translocation