After upgrading to newest versions from this site, I got the following messages:
You are using The Events Calendar PRO but your license key is out of installs. Visit the Events Calendar website to manage your installs, upgrade your license, or purchase a new one.
There is a new version of Event Tickets Plus available but your license key is invalid. You may need to download and manually install the new version. You can check the status of your licenses and download plugins by logging in to your account on theeventscalendar.com. View what’s new with version 4.5.1.
BTW, I have never put in any license keys before, and they worked just fine.
Anyone else has encountered the same problem? Is there a way to fix it?