[MM3-users] Adding user - Error 409 Subscription request already pending

We have a couple of people trying to subscribe to our list but receive an error similar to: {"title": "409 Conflict", "description": "Subscription request already pending"}

If I try to Mass Subscribe them in Postorius I get this error: HTTP Error 409: b'{"title": "409 Conflict", "description": "Subscription request already pending"}'

In Postorius I don't see them hung up in Subscription requests.

What to do?

Thanks, Kevin