Can't Book Events After Recent Update

Events Manager 5.5.6
Events Manager Pro 2.3.8.1

Since updating the plugin yesterday I am no longer able to book events. When clicking the book now button we get the spinning wheel that never stops. Worked great before updating. Any ideas?

You can see the problem at: https://academyofdes.org/wp/events/comprehensive-esthetic-rehabilitations-design-techniques-and-materials-by-dr-gerard-j-chiche/

https://www.ads-software.com/plugins/events-manager/