Family account screen time requests stopped working on iPhone

My son’s iPad is linked to my account and we have screen time limits. He has to send me requests for any extension of his iPad screen time and these notifications have stopped working on my iPhone. They still pop up on my iPad.

I cannot see any difference between my iPhone and iPad account settings.

I have tried turning my phone on and off - this works temporarily ie notifications come through, but the next day the notifications stop.

Please can some one help me get the notifications working on my phone again.