Re: When a campain is over, how can I restart it?
In your campaign setting page, down near the bottom under advanced settings you should see schedule, start date, end date. If your campaign has ended you are able to edit the end date here.
If you are unable to see the advanced settings, check the campaign type. You need it to be "all features" to see the advanced settings.
Is the campaign ended or just paused? If it's paused you can click the box to the left of the campaign name and change this to enabled.
Let me know if this fixes your problem.