Issue sending previous campaign to a contact

I was wondering if anyone else is having issues sending a previous campaign to a contact? The contact meets the criteria and segmentation for the original campaign, but I just get an error message saying “message not sent”.

I’ve raised a ticket with support, and they’ve just said they’re looking into it. I thought it was just 1 contact, but its across many and multiple campaigns.

Keen to understand if this is a general issue, or just with our account?

Campaign or automation?
Through different process, I’ve recently had similar issue, but in automation. In an automation, you can open it through the contact and see their specific path… and if an email wasn’t sent, you can hover over the error and it will pop up a window to tell you why - except the reason why might not be correct! Nevertheless, might be starting point.
One thing to check is to make sure the contact is “Confirmed.” In their contact record, where it says the name of the list they belong to, it should have a green checkmark. If not, click on it and it will show what their status is. If “Unconfirmed,” then they never fully authenticated (a whole other issue), and AC won’t send them any emails until they’re confirmed. I’ve just discovered that I have a whole host of contacts that were considered unconfirmed (because I didn’t even know that 2 factor authentication was on!) and that they haven’t received any email from me since they subscribed - in some cases, for years!
Hope that helps…