If you are running an AutoCAD-based product, the most common error messages are listed, with links to their solutions, on this Knowledge Network page.
If you have a network license and see a FLEXnet error, the most common codes, and descriptions of the underlying problems, are listed on this Knowledge Network page. Additional information on FLEXnet errors and solutions is available in the License Administration Guide, a PDF document that is installed with the Network License Manager. On Windows, go to the Network License Manager directory; on Mac OS X or Linux, go to the flexnetserver directory.
If you need additional assistance, go to the Installation and Licensing Knowledge Network page.