works on MacBook, other iPhones, and Android devices, but it does not work on my own iPhone.

Because Teams works with the same accounts on other devices but no account can sign in on this specific iPhone, the issue is almost certainly device/app configuration on that iPhone rather than the account.

Try these steps in order on the iPhone 14 Pro Max:

1. Confirm Teams version and iOS version
   • Open the App Store → search for Microsoft Teams → make sure it is updated.
   • Teams mobile sign-in behavior described in the documentation requires at least:
     • iOS Teams version 2.0.13 (build 2020061704) or later for standard sign-in, and 6.6.0 or later for domain-less sign-in features.
   • If iOS itself is very out of date, update iOS, then retry.
2. Fully sign out and remove Teams from the device
   • If Teams is partially signed in, sign out from within the app.
   • Delete the Teams app from the iPhone.
   • Restart the iPhone.
   • Reinstall Teams from the App Store and try to sign in again.
3. Check if device management or app configuration is blocking sign-in
   If this iPhone is managed by an organization (MDM/Intune or similar), Teams can be configured to restrict which accounts are allowed to sign in:
   • On enrolled iOS devices, admins can set:
     • IntuneMAMAllowedAccountsOnly = Enabled and
     • IntuneMAMUPN = <allowed UPN>
   • When this is configured, only the specified corporate account can sign in to Teams on that device. If the device is misconfigured or the allowed UPN does not match the account being used, sign-in will fail for all other accounts.
   • Contact the organization’s IT admin to confirm whether such a policy is applied to this iPhone and whether the correct UPN is configured.
4. Check for shared-device or domain-less sign-in configuration
   • If the iPhone is set up as a shared or managed device with special Teams sign-in configuration (for example, domain-less sign-in where the domain is prefilled), verify with IT that the configured domain(s) match the tenant being used.
   • Incorrect domain configuration can prevent sign-in from completing.
5. Test with a completely different network and no VPN
   • Temporarily disable VPN or security apps on the iPhone.
   • Try on mobile data and on a different Wi‑Fi network.
   • If Teams signs in only on some networks, provide those details to IT so they can check any network or conditional access policies.
6. If still failing, involve IT or Microsoft support
   • Since other devices work, provide IT with:
     • The iPhone model and iOS version.
     • Teams app version.
     • Exact error message or code shown during sign-in.
   • IT can then review device policies (Intune app configuration, device compliance, conditional access) and, if needed, open a support case with Microsoft.

References:

• How different technologies affect Microsoft Teams sign-in