HomePod Mini stalled at "Setting up"

Hi everyone

I bought a new HomePod Mini for my son last week and haven't been able to set it up - obviously this has been upsetting for my son!

I go through the set up procedure using my iPhone but it stalls at the "Setting Up" stage. I get the "Setting Up" card displayed on my phone with a spinning icon but the procedure doesn't progress from there (see attached image). I've left it like this over night and also for extended periods after numerous attempts but I can't get past this stage. I'm forced to press the 'x' widget and exit the set up.

I've seen questions about this online (and in Apple discussions), but the recommendations haven't worked for me. I wondered if anyone's had experience with the problem and found something that works.

Additional info:

I'm using the latest iOS (15.2) on my phone

I've reset my phone's network settings and restarted my phone

I've reset the HomePod multiple times (pressing and holding the top till three beeps)

I've attached the HomePod to my Mac and manually updated the speaker from 15.0 to 15.2

I've tried using two different WiFi routers/modems

I'd love to get to soled for my son's sake!

Any help would be much appreciated.

Thank you!