My screen will not rotate, after several attempts to solve

Some Apps, annoyingly, are not designed by the App Developer to operate in Landscape screen-mode. This is not the fault of the Operating System, but is instead either “by design” or omission by the respective Developer.

This malady is most often observed in Apps principally designed for an iPhone.

Only where an App is coded to work in both Portrait and Landscape modes can the Operating System display in either screen orientation.

Some third party apps can't rotate.