How add Ckeditor on EntityType field
There are 4 different field types that contain a text


string
string_long
text
text_long


What long means should be obvious, the difference between string and text is that text has a format (like full_html or basic_html) while string is always plain text.

You are currently using string_long, it doesn't make sense to show a wyswiwyg editor for that, since it would always escape all HTML. Use text_long instead.