Cannot get WhatsApp to run after I enter my phone number

Hello,

I have bought a new Iphone 13 Pro Max. I recently backed up my Whatsapp data on my previous Iphone 11 to the icloud and I confirm that the backup is there.

Everything has been transferred to the new phone - except that WhatsApp just won't open! I type in my phone number +44 - then the number) and click the DONE option and it says "retrieving credentials" and then after some 30 seconds, i get the message " .. WhatsApp is temporarily unavailable. Please try again in 5 minutes .."

I have done this three or four times with no success. I have tried removing and reinstalling WhatsApp (not the Business one), turned the phone on and off, checked and rechecked that I'm signed into my Google account, turned WiFi on and off, turned Roaming off - nothing works!

The App still works on my old phone (still with power and on WiFi with no Sim card inside) so I do not know how to solve this. The phone number is the same - I just transferred the Nano Sim from the old phone to the new one.

I'm out of ideas. Any help would be appreciated

Thank you

Lee James
West Sussex UK