If customer has prior Toad installed with a commercial key, installing the version above will add another entry in productlicenses.xml file with exact major.minor version. This makes deleting key in licensing dialog in any version of Toad ( including prior version, the current version and later version) fail at first attempt, you have to delete the key again.
WORKAROUND:
Delete the key again.
STATUS:
Waiting for fix to be released in a future version.