Authentication Loop Between Microsoft Teams and Authenticator on iOS

Question

I have a corporate Microsoft 365 account that uses two-factor authentication (2FA) with the Microsoft Authenticator app.

When I try to sign into this account on the Microsoft Teams app on my iPhone 15 Pro Max (running iOS 18.4), I encounter a persistent login issue. The Teams app automatically redirects to the Microsoft Authenticator app for approval, but immediately after Authenticator opens, it switches back to Teams. This triggers a continuous loop between the two applications, making it impossible to complete the sign-in process.

Troubleshooting Steps Already Taken (without success):

• I have tried removing and re-configuring the 2FA method by scanning a new QR code.
• I have also completely uninstalled and reinstalled both the Microsoft Teams and Microsoft Authenticator applications.

The issue persists despite these efforts.

Answer 1

Dear Ngà Phan,

We sorry to hear about your experience. Is this situation happen to other app? Are you a user or admin? 
 
If you are a regular user in your company: 

Please contact your IT administrator and ask them to revoke and require re-registration of MFA for your account. They can follow these steps: 

1. Sign in to the Microsoft Entra admin center as an Authentication Administrator.
2. Navigate to: Identity > Users > All users.
3. Select your account, then choose Authentication methods.
4. Click "Require re-enrollment of multi-factor authentication".

This will reset your MFA settings, and you’ll be prompted to set up a new authentication method (e.g., a new authenticator app) the next time you sign in. 

If you are the admin (or the only admin): 

If you cannot access MFA and have no other admins to assist, you can: 

1. Create a new tenant account (temporary solution):

• Visit Microsoft 365 Enterprise Plans and select any plan to start a free trial.
• Follow the setup process to create a new tenant.
• Once set up, submit a support ticket via:
• Microsoft 365 Admin Center > Support > Help & Support
• Or directly: https://admin.microsoft.com/#/support/requests
• Remember to cancel the trial after resolving the issue to avoid charges.

Let me know if you need further clarification or assistance. 

If you are a user of a personal account, you can find your help at: 
If it still didn't work, you may reach out to Microsoft personal support  

1. Go to https://support.microsoft.com/contactus   
2. Choose Office > Get home support 

3. EnterOffice or your issue in general in the box below "We're here for you" then click "Get Help  
4. Scroll down and click on Contact Support then log in to your personal Microsoft account  
   If the account cannot be logged in, you can use another account or create a new account to execute  
5. Select "Microsoft 365 and Office" in Products & Services, select "Technical Support" as a category, and click Confirm  
6. Select "Chat in a web browser and support specialist" to enter the chat window  

If my answer is helpful, please mark it as an answer, which will definitely help others in the community who have similar queries to find solutions to their problems faster.  

Thank you for your kindness and understanding! Please let me know if you need anything else.  

Best regard, 

Sophie N - MSFT | Microsoft Community Support Specialist

Answer 2

Hi Sophie,

I am administrator, i did some thing like:

Actions taken from the Administrator account:

1. All of the user's registered MFA methods have been deleted.
2. The "Revoke sessions" command was executed.
3. The "Revoke and require re-registration of MFA" command was executed and completed successfully.

Results after user re-configuration:

• The user was able to sign in successfully via a web browser.
• The user completed the MFA setup process again using the Microsoft Authenticator app on their mobile device without any issues.

Persistent Issue:

• Despite the successful MFA reset, when the user attempts to sign into the Microsoft Teams mobile app, the exact same authentication loop error continues to occur.

Reference Material:

• A video recording of the error is available at the following link: StartFragment error.mp4EndFragment

Answer 3

I am having the same issue as described and it began within the past 7 days although I can't recall the exact day.

the only solution I've found to breaking the loop is signing into my company profile in edge for iOS and then teams will Auth properly but within 5 minutes, Edge will kick my profile out and teams will begin the Auth loop again.

Answer 4

HI Sophie,

Is anything update about this case? Please let me know. My user stuck and can't use on iphone.

Answer 5

Dear Ms. Ngà Phan, 

I want to sincerely apologize for the delay and any confusion caused by my previous message. It seems there was a technical issue that prevented me from reaching out to you privately, and you may not have been able to see my message. I truly understand how frustrating this must be for you, and I deeply appreciate your patience and understanding during this time. 

I have just sent you a private message, and I kindly ask you to take a moment to review it when possible. This will allow me to check the status of your case and ensure that it gets the immediate attention it deserves. 

If it's not too much trouble, would you mind checking your private messages? I believe it will be easier to have a more detailed conversation there, and I’ll make sure we address your concern thoroughly. 

To view your private messages, please follow these steps: 

1. Go to Microsoft Community and sign in using the same email you used to post your question.
2. Click your profile icon in the top-right corner and select "My Profile."

1. Look for the “View Private Messages” section and click to open the message.

Thank you so much for your time and understanding. I’m here to help and will do everything I can to assist you further. 

Warm regards, 
Sophie N – MSFT | Microsoft Community Support Specialist