Entering a passcode to authenticate my iPad iCloud sign-in

I'm setting up my wife's new iPad and, at the iCloud sign-in stage, it shows a pop-up on her iPhone to allow the sign-in, including a one-time 6-digit code. I enter this and then I'm subsequently asked for the passcode to that iPhone. I've entered this correctly (I've verified on that iPhone) but get the message that this is an incorrect passcode. The net result is that I cannot sign into iCloud on my wife's new iPad despite being able to validate all info is correct. Has anyone encountered (and resolved) this issue?