Hey Virginia,
Thank you for reaching out to us!
I’m sorry to hear that you are experiencing this issue, let me help you to solve it!
The 500 Internal Server Error is a very general HTTP status code that means something has gone wrong on your website’s server, but it could not be more specific on what the exact problem is. This status code is usually associated with a PHP Fatal Error, so to identify the cause of this issue, I would recommend you to temporarily enable WP_DEBUG and WP_DEBUG_LOG and share with us any messages you see while trying to activate Events Calendar PRO. All WP_DEBUG messages will be stored in a debug.log file in /wp-content/debug.log.
Thanks!
Patricia