WhatsApp initialization on new Android phone

Hello,
I just bought a new phone and installed WhatsApp.
Everything seemed to be working fine at first - they asked for my username & optional picture - but it has now been saying "initialization in process" for almost 6 hours...
And now I've tried contacting the helpdesk and it just says "connecting", even though I have a good wifi connection.
Does anyone know how to solve this issue ?
PS : the phone I'm using is a Xiaomi 11 Lite