Screen rotation no longer works on iPhone7+ after recent ios update, no longer goes into landscape display mode when I want to view a picture or video. I see a new icon on top of my display and I believe it is related to screen orientation. Help?

Screen rotation no longer works on iPhone7+ after recent ios 11.4 update, no longer goes into landscape display mode when I want to view a picture or video in portrait. ios 11.4 crippled the best feature on my phone, why is that? I see a new icon on top of my display and I believe it is related to screen orientation. When I go into settings I do not see any way to adjust screen orientation back to what is a great feature. Seems like a bad idea to screw up something that worked well and is a great feature of any modern phone or tablet. I have restarted the phone over 10 times, the display stays locked in portrait mode and does not go landscape. Losing this capability is deeply disappointing and I will be off my contract in 3 months. If fixed by updates soon, then I can be patient. If it does not get fixed then "hello, galaxy".