Noticed this in the last event that counted for Campaign III and confirmed it again today.
When you complete a TFO for the event, there are 2 separate timers that start running. One is a 5 minute timer to choose a reward. The other is a 2 or 3 minute timer for when the map closes.
Choosing a reward will give credit for the Pahvo event (as long as you have it available for the day, of course), but if it is not chosen within the 2 or 3 minutes of the MAP timer, you will NOT get the 50 points of progress toward the campaign. You can't get it by running another TFO, either. You will need to wait for the next day.