UE not sending register request for VoNR (although supporting all VoNR related functionality)

Hi Experts.

What can be reason UE not sending register request for VoNR but support all VoNR related functionality?

Maybe you don’t have IP Voice prefered in preferences in attach request.

That is checked: it’s there.

I’m thinking some binary file needed for new service.

Have you checked UE profile in Core?
Is it provisioned to use VoNR?
Also thinking about it, is APN defined in settings?
Some handsets are weird that they don’t trigger IMS attach unless you add APN.