Cannot sign in player 2 on split screen...

Hello,
Firstly, accept my apologies as I am a novice with games consoles so this issue is probably quite easy to fix, so here goes…

I have just bought a wired controller to play Forza 7 against my daughter on her Xbox One. We have created an Xbox profile for me and assigned the controller to my account. I have also signed in to the dashboard, so we are both signed in. When she selects split screen and I press the menu button to sign in nothing happens. I know this button works because it cancels the car screensaver, so I am fairly sure the controller works ok.

Any ideas as to what I am not doing right?