I have the same problem OP. It was working fine but this morning it stopped rotating in gallery when I tilt the phone. Tilt still works when taking a picture and everywhere else.
If I manually rotate the image it fills the screen but scrolling is then top to bottom and I have to manually do it for each image, plus when transferring to desktop images are sideways.
Update* I fixed it. I had screen rotation turned on in the deep settings menu, but that quick bar settings you see when you swipe down, rotation was turned off there. The funny thing is that rotation still worked in most places, just not in gallery and web browser.