Update Apple ID settings, some account services not a available until you sign in again?

I recently added my new iPhone 11 pro to the account I used for my iPad Pro so as to sync all my online data between both, changing over two stage password verification as well, but now cannot get into account thru my iPad and it asks to update with the above statement, which when I access it off Settings Icon, seeks to change the account password, which would surely lock out the 11 pro? Looked on line for solution, still looking...