Hey @Angie56! Sorry for the trouble! Did you ask them if they checked their spam folder, just in case?
I'd recommend reaching out to our team at firstname.lastname@example.org (or via the in-app messenger in your account) with a description of the issue and the email addresses of the subscribers who didn't receive it (and let us know which email it was they didn't receive). We'll take a look and make sure there are no deliverability issues at play here :)