Events Manager problem: Bookings not possible from mobile device

Events manager works fine on a desktop, but booking from a mobile device won’t work. Either it keeps spinning, or there is an error message (explaining you need to choose a # of tickets, but that choice was made).

I’ve changed up the mobile device themes and doesn’t seem to make a difference. And even a non mobile theme used on a mobile device doesn’t allow for bookings.

Any solutions?

PS: site = uwfrenchhouse.org
PPS: I’m not a developer. I’m a French teacher. Go easy on me.