Clients Unable to Sign-Up

The form looks great on the backend and the frontend. However, the plug-in simply does not perform well consistently. One address will be accepted, but the second one will not. The third email address may or may not be accepted, then the fourth one will not.

There is a very long forum with similar complaints. The only solutions given were the disable-everything-else-on-your-website-then-create-a-new-event-on-getresponse/mailchimp-and-if-that-does-not-work-then-it’s-them-and-not-us kind of response.