Try to update your iOS to the latest version. Another option is to disable the 3 spotlight search options, restart your phone and check. For some reason, this trick often takes a few hours before it works.
Also, force restart your iPhone. Hold down Power button and the volume down button until the Apple logo appears on the iPhone 7 screen.
Go to Settings → General → Reset, and then select “Reset All Settings” to see if that fixes the problem
Go into Settings / Photo & Camera, and then “Preserve Settings” under Camera. Turn “Camera mode” and “Photo filter” off, and leave “Live Photo”
Some people suggest that Assistive Touch causes this problem. SO be sure to turn it off via Settings > General > Accessibility > Assitive Touch
Try and change the 60fps on in the video settings to something lower like 1080p at 30 fps or 720 p at 30fps. Go to Settings > Camera
If these tips still do not solve your problem, you may try to contact Apple support. Since you’re using an iPhone 7, it should still be under the first year of Apple Care+. But don’t wait too long, remember that the free Apple Care last only 1 year from date of purchase, unless you purchased the additional year of support.