Used T23G, can't factory reset, can't update

[MonkeySeeMonkeyDo]

I bought a used T23G, I boot it up and it is provisioned and working... I factory reset the phone I am able to login to the web interface with the default credentials. I update to the latest firmware, the phone restarts, the firmware did not update (same version as before) and the phone reconnects back to the old provisioned customer.

I have no idea what is going on. I have no factory reset it from the phone, and from the web interface, but at the end it always goes back to the old provisioned settings.

Any recommendations to try?
TIA