iPhone XS Max's iCloud Activation Error 400 after Factory Reset

so I signed out of my iCloud on my iPhone XS MAX turned off passcode and forgot to turn off find my iPhone after factory resetting its asking for my iCloud by refusing it how can i fix the problem? so I tried connecting it to a computer with iTunes and it brought a message saying this iPhone is locked to the owners iCloud I tried deliberately putting a wrong passcode or iCloud it said wrong password but when I enter the right credentials its bring an error 400 and telling me to try later and when i try to activate the phone manually its not passing the next option after entering email and password but when I enter a wrong password its detecting so am confused how can I fix this problem iv suffered enough

[Edited by Moderator]