All of a sudden my way point missions won't load. I select a saved mission that I have flown before, press load and GO and message flashes up "Mission failed to load". and the Mavic does nothing. Any ideas how to fix this?

Wish i knew how to help you............since that app is not supported here i'm not sure you will get any help actually.

That happens most often when the bird is too far away from the RC. Be sure you have your drone fairly close (20-50 feet) from your RC when you upload your mission. If the mission starts farther away from you and you don't want to the drone to automatically fly to the starting point, you can always upload first, fly manually to the destination, then start the mission. Also, if there is magnetic interference that can affect the upload process. Another option is to log out of Litchi completely, turn everything off, then start everything up again and log back in to Litchi. If none of this works, you can try reinstalling the app or sending an email to Litchi support. Also, you can go to the MavicPilots forum and ask there - there are a LOT of Litchi pilots on MavicPilots.