Outro didn't export?

[NotJustBlonde]

I created an outro where it was a black screen, the text was a window to a shot from the video (I used a luma key and inverted it) and I added picture in picture clips of other videos I've made. When I export things, they don't let me see what i've exported until I've uploaded it. It's worked every time for me except the last video I made - the outro disappeared completely. I definitely exported that section of the timeline because the audio for it was there, and I definitely selected 'export all layers' or whatever that button is called.
Can anyone tell me why this has happened?

 

[skenkee]

Can't tell what happened. It's hard to tell what happened. It might help if you add a video example or screenshots.