By default body field of a content type will not be shown among the fields to index, which is kind of strange but that is how it is as many other properties and fields of content are there by default. To add it, you will need to go to bottom and use "Add related fields" and find it there, again you would expect some machine names there to find fields but they are not used and for body field there is specially strange name to use "The main body text" which does make sense, but if you have big amount of fields you wouldnt look for it under letter T, so it is a bit odd, but once you find it, it does work.