Contact Form 7 Not Working

As recently as Monday morning, our website’s Contact Form 7 was working correctly. I know this because I received a form that morning.

Thursday morning, our sister campus emailed me saying that they are not receiving contact forms. There have been no changes made to any settings.

When I tested the form on our website, I received a message that it was sent successfully with the green border. However, I have been waiting for receipt and it has not showed up in either my inbox or junk folder.

Any suggestions? I’m not very advanced in my WordPress knowledge, so please make sure to ELI5.