ERG mode is not active in free ride.
Is what you are saying that you are no longer getting variance in resistance from the trainer on hills etc.?
Try disconnecting and reconnecting “controllable” or whatever it’s called when you connect everything as you boot up.
Also check your “trainer difficulty” in settings once in-game is not set to 0% (slider all the way to the left) as this disables resistance changes on hills.
edit: or might be related to this if using apple tv: Zwift resistance, hills etc working fine on windows, not iPhone or Apple TV