The rear camera has to be on for it to work. If you have the front camera on it'll grey out.
Sent from my SM-N9005 using XDA Premium 4 mobile app
// Nexus 5 (D821) // Liquid // UBER //
Note 3 (SM-N9005) // AOSP ROM of variety // Lean or temasek's Kernel // - Dumped. No more Samsung