Apple watch playing no sound

Hi,

I've just got a brand new Apple Watch SE which I've only had for 2 days and it has randomly stopped playing any sound at all including calls, notifications, Siri & 'find my'.

I have checked all my sound and app settings, bluetooth, and do not disturb, updated the watch and my phone, restarted both and unpaired it from my phone but nothing has worked. It is working totally fine otherwise but I have no idea what I've done.

Any thoughts on what it could be?