Enterprise Reporter 2.6 and later requires a new license file format (.dlv instead of .asc). This can cause an issue after an upgrade has completed as the Configuration Manager will not load without the new license file applied.
The following may occur if you try apply an ASC license key file to 2.6 or later:
"The selected license file is not valid. Please select a valid license file or contact your sales representative to obtain one"
Contact the licensing department to obtain a new license file. There is no additional cost for a new license file.