Dear Keith,
Thank you for reaching out!
I’m sorry about the delay in the reply. We are a bit overloaded at the moment due to unexpected sicknesses in the team. We are doing our best to work through the incoming requests as soon as possible, and we definitely try to keep our promise of replying to every post within 24-48 hours as per our support guidelines, just like in your case.
I have tested the event url you shared with me with all the browsers (recent versions) I have on hand (Firefox, Internet Explorer, Chrome, Edge, Safari for Windows) and I succeeded in submitting and RSVP in all cases without any issues.
Are you still experiencing the issue or did you manage to solve it somehow? Did you change anything in the setup?
If the issue still exists, does it also happen when you deactivate WooCommerce? Does it happen with a non-beta WooCommerce?
Looking forward to helping you solve this.
Cheers,
Andras