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Hi,

AutoCAD for Mac is not compatible with OS X 10.11 at the moment.
The solutions are:
- roll back to Yosemite. (I think the Update for AutoCAD will be released soon, but don't know exactly when.)
- another way is to try this:
http://forums.autodesk.com/t5/autocad-for-mac-general/autocad-for-mac-public-beta-available/td-p/579...
Beta works on El Capitan.

Maxim