Whatsapp back up

I have upgraded my phone to iPhone 14 pro max. It has been a nightmare. WhatsApp does not back up except at the Apple Store. As weird as it might sound. I was able to back it up while sitting at the Apple Store and then after installing IOS update 16.2.

I deleted the application and installed it again. I reseted my network settings. I signed off iCloud and signed back.

I am desperate. Went twice to Genius Bar, no solution. They asked to contact WhatsApp. WhatsApp asked to talk to Apple. Blaming each other with no solution.

Anyone facing the same problem?