Great question! If you sent the invite through your event you will want to find and click on the name of the Event in your account. Make sure you're on the dashboard view and scroll down until you see "Emails". Click on the number of emails sent and then the number of opens on the right of the invite in question.
Hope this helps,
Hannah M. Community and Social Media Support
If you find my post helpful, and it answers your question, please mark it as an Accepted Solution