Hi Justin!
Thanks for reaching out to us. I’m sorry you are experiencing that issue. Let me help you with it.
First, please let me note that you should still be able to use Events Calendar PRO without activating the license. You just won’t be able to get automatic updates for it, but you can always download the latest versions of the plugins from your downloads page > https://theeventscalendar.com/my-account/downloads/
On the contrary, you do need a valid Event Aggregator license being active on your site to be able to import from other sources like Facebook and Google Calendar.
The key validation server is not available error message could have been a glitch, so could you please try deleting the license key from your site and save, then try pasting it again and save? Does it change anything?
You can check the Event Aggregator System Status by going to your wp-admin > Events > Help.
When coming back, please share with us your system information by following this guide > https://theeventscalendar.com/knowledgebase/sharing-sys-info/. We’ll see if there is anything strange that would indicate an error from there.
Thanks,
Victor