For some campaigns, once you de-activate it once, it cannot be re-activated.
In these cases, you can "Duplicate" the campaign and (essentially) activate a new campaign with the same contents.
To do this, you'll go to the campaign and click on "Edit" in the top right hand:
Then click on "Duplicate" in the top right hand of the next window:
If further assistance is required, submit a ticket to Punchh Support. (For help submitting a ticket, click here)