First Response Disappearing line?!

Ms. Velociraptor β€’ πŸ’“πŸ’™πŸ’™ Baby #4 due in December πŸ’š
I took this First Response this morning and there was a line right away. Buuuuut it disappeared at like 7 minutes.
What does this mean? Positive? Negative?
First pic is at 3 minutes. Second pic is at 7 minutes.