Can’t see messages after blocking someone

Messages can be blocked by their phone number as well as their email address. Since you can see them on your watch, it sounds like the email they used for messaging was blocked as well. Review this support article to see how to get to the blocked number/email list depending on the app. If you also have the person in your Contacts app, you can go there to see if they are blocked there.

Sorry, I forgot to include the Support Article:

Block phone numbers, contacts, and emails on your iPhone or iPad - Apple Support

So, are you saying that, since you have unblocked them, they have sent you new messages and you haven't received them? You won't see messages they sent while they were blocked.