My Apple ID PASSWORD fails at OS9.2.1 install?

I'm logged into my new iPad, it tells me a security software upgrade for os9 is needed. When I go to "install" it from the settings section, it asks for my passcode so I reenter my Apple ID but it keeps failing, I know I am typing it properly, why is it asking for a passcode here? Which passcode ? I thought the apple id password was for everything?

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