Unable To Edit Terrain

Hello, I am very new to Unity (as in no scripting knowledge) and I recently tried to use the Raise/Lower terrain feature, and when I did I was unable to raise or lower the terrain. I had at one point been able to raise the terrain, but after following a lesson in my book and setting my height to 30 and using the flatten button, I was unable to raise, or lower the terrain. I did not do any scripting, I just added the terrain object and resized it to 1000 x 1000. No other changes were made.

P.S. Even after deleting the project, and starting a new one, I still am unable to raise or lower the terrain, please help!

The only time I’ve seen something like this, it’s been because I’ve baked the lightmaps and therefore the shadows on the terrain don’t move, so it looks like editing isn’t working. Window->Lightmapping->Clear will clear lightmaps if there are any.

Also, set your brush opacity to 100 just to be really sure it’s not working.

It seems like settings my opacity to 100 fixes the problem. I’m a bit confused though because in my book (Unity Game Development Essentials) it says to set my opacity to 0.5. However, when I attempted this, I was only able to set it to even numbers (1,2,3,etc.) and when I set it to 1, none of my changes with the raise/lower terrain brush had any effect. So my question is, has Unity changed the way the height adjuster works, or is there something wrong with the directions?

P.S. my book is teaching me to create an island by setting the height of the 1000 x 1000 terrain to a height of 30, flattening it, and then using the raise/lower terrain brush to create the outline of the island.