I am unable to rotate the screen on iphoneXR

We have no idea what suggestions you have tried, because you haven't told us.

Have you checked Rotation Lock? Open Control Center by dragging down from the upper right corner. The rotation lock icon should be a dark color. If it is a light color with a red icon then it is rotation locked.

Are you aware that not all applications support screen rotation? The Home screen on an Xr does not, for example. To actually test open the Photos app and view a photo. The image should rotate if you hold the phone vertically and turn it between portrait and landscape mode.