The Pi4 doesn't support the rotate_display parameter anymore - see https://www.raspberrypi.org/documentation/configuration/config-txt/video.md. At some point, it was possible to use display_rotate=2 to flip the screen, but after a firmware update this year, this is also no longer supported.

There is some guidance on how to rotate the display on the Pi4 here or at a similar post here in the forums.