With AutoCAD 2015's BorrowLicense command, AutoCAD is supposed to end the license on the current machine even if you are connected to the network with access to the FlexLM server. However, while working in AutoCAD, you may see this alert box a few days after the borrowed license is expired or returned to the server.
Then you'll get a couple more alert boxes.
Then AutoCAD will close itself.
To fix this issue, be sure to delete these two registry keys after returning the license to the server or when the license's borrow time is up.
Note: If you have more than one borrowed AutoCAD release license, you must delete only the AutoCAD version borrow key and leave the "infoborrow" key as is. Unless all lienceses are returned or ended -- then you must delete all keys.
Notes from Cadalyst tip review R.K. McSwain: Although we don't have the means to test this tip, we trust frequent contributor Andrea with this information regarding returning a borrowed license. Use caution when working in the Registry Editor.