A campaign can be scheduled, running or paused.
If the campaign in on paused for a prospect, it means that this prospect will not receive the next step of the campaign as the campaign is momentarily stopped.
When a campaign is pausing, mostly of the time it is due to your sending address disconnection.
When your sending address is disconnected, you receive an email.
Here is what you need to do:
1. Go on your sending address page, click en reconnect (or on actions and then credentials).
2. The campaigns have now to be restarted one by one from https://app.prospect.io/campaigns. Select the prospects and click on resume.