Ajax not working?/spinning wheel permanently without sending

Hey guys, not sure what’s happened but all my forms have suddenly stopped working.

https://melbacademics.com/workshops/methodsworkshop/

That’s a link to one of the forms, and when I submit it just comes up with the spinning arrows and nothing happens; no email is sent, etc.

I’ve tried deactivating all plugins and going back to 2011 theme but it still doesn’t work there.

Any help?

Cheers!

https://www.ads-software.com/extend/plugins/contact-form-7/