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Hi Laura,
Which OS X do you have on your Macbook Air?
Keep in mind that AutoCAD for Mac is not supported on MacOS Sierra for the moment.
If you have supported OS, than try to Clean reinstall of AutoCAD as described here:
https://knowledge.autodesk.com/support/autocad-for-mac/troubleshooting/caas/sfdcarticles/sfdcarticle...Than try install AutoCAD again and don't forget to apply all Updates.
Maxim
