Generic Type Challenge task 5/5: Almost got it... Can you figure out what I'm doing incorrectly?

I followed the instructions pretty closely. And the preview gives me no errors; but my code is still not passing. I believe my issue is in the final method dequeue(). I know it needs to remove the first item of the array and then return that same item. I think thats what my code accomplishes; but for some reason it won't let me pass. Any feedback will be greatly appreciated!!

Add a second function named dequeue, that takes no parameters, and returns an optional Element. Since a queue follows a first in, first out policy, dequeue returns the element that was added first. If the queue is empty, return nil For example, given the queue: [1,4,9,7], calling dequeue returns 1, and the resulting queue is [4,9,7]. Note: Dequeue removes the first element from the array

struct Queue<Element> {
    var array: [Element] = []
    var isEmpty: Bool {
        if array.count == 0 {
            return true
        } else {
            return false
        }
    }
    var count: Int {
    return array.count
    }

   mutating func enqueue(_ Element: Element) {
    array.append(Element)
    }

    mutating func dequeue() -> Element? {
      if array.count < 0 {
      var removedItem = array.remove(at:0)
      return removedItem 
      } else {
        return nil

    }
 }
 }