Why isn't the Google Event Calendar on my Wix site displaying my calendar content?
In order to use the Google Event Calendar app, please make sure to set your Google Calendar settings to the Make this Calendar Public option and choose See all event details from the drop-down menu.
If you have a Google Apps email account, you may need to contact your Google Apps Administrator before you can set your calendar to Public. For more information about how to set your calendar to Public, click here.
In addition, please make sure that you are using a calendar that is owned by you and not one which has been shared with you.