Follow these steps to troubleshoot the issue:

1. Check your phone’s settings: Make sure screen rotation is enabled through the display settings.
2. Verify that the auto-rotate feature is turned on: Go to Settings > Display > Advanced > Auto-rotate screen.
3. Restart your phone: Sometimes restarting can refresh the software and solve problems.
4. Check your phone’s software: If the software hasn’t been updated in a while, it may be the reason the screen isn't rotating.
5. Make sure you are not locked into one app: If an app doesn’t support the auto-rotate feature, the app may override the device setting.