Apologies for the trouble. Please note that AutoCAD LT for Mac 2015 is not supported on Mac OS X Sierra. Have you considered moving to the most current version: AutoCAD LT for Mac 2017, which is supported on Sierra. This should resolve your issue and is included with your subscription.
Matt DiMichele
Autodesk Product Blogs | @ADSKCommunity Twitter
Likes are greatly appreciated. Everyone enjoys a thumbs up!
Please Accept As Solution if this resolves your issue, to help others benefit and locate it.