Hello @PennieS0 ,
Let's start by having you disconnect the social media accounts from the Constant Contact end, as well as from your social media's ends. Then, when you've also confirmed you're logged in as the social media pages' admin, go ahead and reconnect them. If the issue persists we can do some more advanced troubleshooting, but let's start with the total permission reset method.
Have you already completed the steps listed above and confirmed that you are an admin? Sometimes selecting repair isn't enough to reset social share and allow it to post again. Can you also reply back with a screenshot of the error you are receiving? Thanks!