Unable to use two-factor authentication on iPhone 15 due to an associated iPhone 4

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Level 1

4 points

Unable to use two-factor authentication on iPhone 15 due to an associated iPhone 4

Hey so at this point I’m going to rely on the internet my support agent is super helpful/insightful but seems we’re both just as confused. For some reason after updating my phone I’m not able to use 2FA. I have an iPhone 15 and we’ve come to the point where the problem may be an iPhone 4 I used to own. I don’t have the phone or it saved on my side but Apple still has it as I guess my phone. Any suggestions on how to fix this?

[Re-Titled by Moderator]

Original Title: 2FA

iPhone 15 Pro, iOS 26

Posted on Oct 4, 2025 1:19 PM

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Answer 1

sberman

Level 10

271,780 points

Oct 4, 2025 3:35 PM in response to Tired3x

The iPhone 4 pre-dated two-factor authentication and used two-step verification. But the switch to two-factor authentication was done by Apple so long ago (I think about ten years ago), that the reference I provide below is currently archived and therefore may be obsolete.

See “How do I turn off two-step verification?“ here.

Two-step verification for Apple Account - Apple Support

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