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Hi Nicholas,

Have you installed AutoCAD LT 2017.2 Update?

https://knowledge.autodesk.com/support/autocad-lt-for-mac/downloads/caas/downloads/content/autocad-l...

It fixes compatibility issues with macOS High Sierra.

If yes, then try at first restart your Mac, if this will not help, then try to Reset AutoCAD: hold down Shift key while you pick on AutoCAD icon in Dock to launch it.

Maxim