Hi,
this is just a heads up on the following. When registering the API key on wp-admin/options-general.php?page=kt_api_manager_dashboard&tab=kt_api_manager_dashboard I looked up the email at kadencethemes.com/my-account/ This page showed the email when I purchased the license 2 years ago. Turned out that I could not use this mail.
I had changed my mail at *Login to see link some weeks ago. Using this other (not listed) mail it worked.
But you should change the documentation about the API keys so that it reads: Use the “API License Key” from kadencethemes.com/my-account/ and your kadencethemes.com login email for “API License email”.
PS BTW, I think a yearly licence would be appropriate (instead of lifetime). I would definitely not mind. Your support is fantastic, the product too. It would still be extremely good money for the value. I am saying this as a very confident customer! I am also a developer and I do know how time-consuming good support is. Especially since you all always answer within a few hours only. I am also very astonished how you manage to do such a good job to so many people.