Default HDR+ Icon gone

Hi guys...
I have my Nexus 5 for 2 months and I am using the newest version of Android Kit Kat (OTA) and stock..
The problem is, the HDR+ icon is gone, can't use this anymore (I've used this 2 weeks ago), tried to clear data/cache of the camera APP , flash is off, still no icon...

Any solution?
Thanks!!!

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