Entries only received via email when sender logged in

I was notified that their contact forms entries stopped being received via email. I tested each of the forms (while the browser was logged into the site), and they received my entries. Later they were told others new entries still were not being received via email.

I logged out of the site and filled out and submitted the forms, those entries were not received via email. Is this something that has been encountered before? I googled the issue and didn’t find anything so any insight is appreciated, thank you in advance for any suggestions.

The page I need help with: [log in to see the link]