I'd greatly appreciate any thoughts! When I physically rotate my U2414H monitor from landscape to portrait or vice versa, the computer display doesn't automatically rotate, (meaning I have to manually elect to rotate the display). It used to automatically rotate - I'm not sure what changed. I reinstalled the driver - not sure if that would help. I also reset the monitor to factory settings. I'm using it as a second monitor connected to a Dell laptop.
First of all make sure Dell Display Manager is installed and running - its DDM that changes the Windows screen orientation to match the monitor orientation.
But here's the thing: on some "auto-rotating" Dell monitors the Windows screen orientation is determined by the physical orientation of the monitor, while on others it is determined by OSD menu orientation. With the U2414H I believe you have to manually change the OSD menu orientation to trigger an automatic change in Windows screen orientation.
Look for a "Rotation" setting under "Menu settings" in the OSD menu and if you rotate the display frequently, consider assigning "Rotation" to one of the OSD menu shortcut keys.
Most likely, windows update changed the video card driver which is why it used to work, but now does not. I think that the actual windows desktop rotation is controlled by the video card driver, not the monitor? Open the User's Guide page 54.