Hello @SharronB5 ,
Do you know if the contact you're trying to update the email for has been unsubscribed and resubscribed previously? If so, then by Compliance protocols that email address is locked in for the contact, and you'll need to add the updated email address as a new contact. If not, please reply to the @ mention email with the two email addresses in question so we can investigate further.
I checked for unsubscribed and there are none listed as I had removed them with this last update.
Is there a secret list I cannot view?
It sounds like this email address you are trying to update was unsubscribed previously so you will not be able to edit it. You will want to send a Lead Generation Landing Page link to the customer so they can sign up again. Thanks!