Looks like it may have been a reporting delay.
This can sometimes happen when the data is being pulled through the system. Usually as long as you can see Ads on your sites all is good. Reporting usually updates by 8am PST however sometimes it can just take a bit longer to pull through and usually if you wait a few hours it will catch up.
If we see its going to take longer to report we will usually show a notification in the dashboard of longer reporting delays.