Feral Heart

Hello. This is my first time making a map on FH. I have looked at many tutorials for making the height map, then putting it into the map maker. I used Paint.NET. I made sure I had the measurements right and saved it as a .png file, but every time I try to put it in map maker, FH crashes. I don't know what I am doing wrong, so please help me.

Also, I could not find the Greyscale of Paint.NET, so I used B&W. I read online that it was the same as Greyscale. If that's what's wrong, can you tell me where Greyscale is?

~Thanks, Lissy <3