I've experienced this issue in Contact Form 7 where when I hit 'Send', it will display the spinning arrow loop but will not return any errors or successfully send a message (though at this point it should return back an error message since none of the fields have been entered).
It's simply stuck in an endless loop.
In the backend, editing the Contact Form, there are no issues telling me if any of the configuration is wrong. So I'm not sure where the problem lies over here.
Any help is appreciated. Thanks!