You don't need the "/100.0" if you already used @en.to_f / @maxen.
Let's see, @en is the current energy, @maxen the maximum. It's drawing a gradient bar width 144, color type 1 at position @en_x+32, @en_y+3. I don't see anything wrong. Are you sure that you have limited those variables right? Also, if you are using a common event parallel process, have you turned on the precondition switch for it?