Hi Vincent,
Thanks for contacting us!
Can you please access your WordPress Dashboard, head over to Events → Settings, select the Licenses tab at the top of the screen and check if your Event Aggregator license key is in there?
If it is not, you should include it. You will find all of your available licences here.
If your key is already in place and the issue persists, you can follow the instructions in the link bellow for further assistance:
https://theeventscalendar.com/knowledgebase/license-key-out-of-installs/
I hope this helps! Let me know if you need anything else and have a great day!
Regards,
Patricia