You can change fp+ if you miss your time.

[leeserw]

This may have been mentioned. We're here now and we missed our fp time for Space Mountain. I didn't realize we could change it for a later time. Our original time was 3:15-4:15. We decided to try and switch at 7:00 and were able to get Space for 7:20-8:20.

 

[shocker]

We were at DAK 2 weeks ago and missed our FP+ time for Safari. We went to the kiosk and there were no other times available so we were just out.

 

[Robo]

We were at DAK 2 weeks ago and missed our FP+ time for Safari. We went to the kiosk and there were no other times available so we were just out.

As an alternate choice in that situation would be to make a later FP+ reservation for a different attraction.