MyFP+ are too late. What to do?

Using the FP+ for the 1st time, going to MK on a day when crowd level is 8. I booked 30 days in advance but all my FP are for after 6p, and my 3rd FP is for 10:40pm. I was expecting to get FP earlier in the day for 2 reasons: may not want to stay till so late in the park (summer), and wanted to use my 3 passes soon so that I could try and get a 4th, 5th, etc. I wonder if I can try to cancel the latest FP while in the park and get a FP for earlier in the day. It looks like the availability for booking via app/site is different from the availability in the park. Today I entered in the app and the site to to book an attraction for 1 person for same day (today), and a number of them where gone. But then Lines app showed FP availability for most of them. It makes me wonder if a number of spots are not made available for the app/site, and are only available for kiosks. Thoughts?

Do not count on the lines app! If you click on the FP availability link on the home page of the app you will see the warning that it is currently not working! On an 8 day there may be very little availabity. If that late FP is something you want to do and you think you will stay through Wishes ( and then do the FP), I would keep it.

I would just keep checking every day before trip for something earlier. People change plans all the time.