Troubleshooting & help
First, choose Library > Authorize Computer to make sure the Adobe ID used to authorize Digital Editions is correct. If it is correct, contact the eBook provider to reset the activation. See this troubleshooting guide for more information.
You can activate Digital Editions on six devices. If you switch machines or devices, you may get this error when you try to launch Digital Editions. See Authorization and launch errors for Adobe Digital Editions 4.0 on Windows.