Lumia Denim Camera Problem

[Ben751]

I have had two Lumia Icon's and both of them have the same camera issue. I update the phone to denim, and with denim your supposed to be able to activate 4K video by long-pressing the camera button, but this doesn't work on my phone, it just opens the camera. When I first tried it, it did prompt me to restart my phone to get the full effect, and I hit ok, but it didn't restart, and nothing changed. Now that message never pops up anymore and my camera just isn't doing what it's supposed to