[Plugin: Events Made Easy] Error after submitting registration

When a user submits a registration, this error shows up:

The website encountered an error while retrieving https://www.domain.com/events/4/event-url/?#eme-rsvp-message. It may be down for maintenance or configured incorrectly.

The registration still gets submitted and shows up in the admin section, but I’m not sure how to fix this.

https://www.ads-software.com/extend/plugins/events-made-easy/