why won't my new iPhone allow me to restore a backup

Hi all

having issues with using a backup from my old iPhone 6 to my new iPhone 7

backing up not an issue but when i go to download or use the backup to transfer all my data onto the new phone

each time i do it asked for my iCloud password and each time i enter every password I've ever used it still comes back as password incorrect

to say this is getting mildly annoying is an understatement and really don't remember transferring from one phone to another being such an issue in the past

is this something new or is it a common problem or is there a work around that I'm missing ??

any help would be greatly appreciated