Symptoms
After upgrading from an older version of the software, the "This site may be running unlicensed software" error will not stop displaying, though the license key file is in place.
Cause
The license key has not been upgraded to a key for the new version, or more than one license key is in the images folder.
Solution
Log into the AspDotNetStorefront site at https://www.aspdotnetstorefront.com/mylicenses and create a new license key for the new version. Generate the new key and save it on your site as was done with the old key file. Verify only the new license key is in the /images folder.