Set up new iPhone restoring the old iPhone = password to unlock back up required

Hello,

I am trying to set up my new iPhone, using the "restore my iPhone function to set it up and mirror it to my old iPhone, however I am prompted to "enter the password to unlock your backup".

I have tried my mac password and my iTune password but that does not work. I have never set up a password to restore back up.

I have done this in the past seamlessly, this is the first time I encounter that issue.

Thanks