Good evening Daniel and welcome back!
Thank you for reaching out to us.
We are sorry to hear about the issues you are experiencing with the license keys.
I would love to help you with this topic.
my Events Tickets Plus is giving me the message that my key is out of installs. How does this make sense? How/why can I not clone the exact same site without receiving this error message?
This is because the license key is actually also tied to a URL (as you can see here: https://theeventscalendar.com/license-keys/)
That being said, things should still work properly in spite of that message. The only thing that it will prevent you to do is to upgrade on that install.
I believe you might be interested by the following post on that topic: https://theeventscalendar.com/knowledgebase/using-one-license-for-your-live-and-dev-sites/
Let me know if that helps.
Have a great day!
Geoff B.