I keep getting a pop error message 9n155. How can this be resolved?

Question

I have been using Microsoft 365 through my employer on my iMac. Suddenly today (was using the exchange email earlier today) I keep getting a pop up box saying error 9n155. My computer is connected to the internet. I did not do any updates today. I am unable to send or receive email.

Answer 1

Hi @Kathryn Nuss ,

Welcome to the Microsoft Q&A platform!

I'm sorry to hear that you're experiencing this issue with Microsoft 365 on your iMac. Here are a few steps you can try to fix this error:

1. Sign out and sign back in:

• Open any Microsoft 365 app like Outlook.
• Go to File > Account > Sign Out.
• Close the app, reopen it, and then sign back in.

2. Clear your credentials:

• Open Keychain Access on your iMac.
• Search for any entries related to Microsoft Office and delete them.
• Restart your computer and try to sign in again.

3. Even if you didn't update manually, it's a good idea to check if there are any pending updates.

• Open any Microsoft 365 app and go to Help > Check for Updates.

4. Sometimes creating a new profile can fix the problem.

• Open Outlook > Preferences > Accounts > + to add a new account.

5. Download and run the Microsoft Support and Recovery Assistant to troubleshoot and fix the problem.

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Please feel free to contact me for any updates. And if this helps, don't forget to mark it as an answer.

Best,

Jake Zhang

Answer 2

Hello, today I had this issue and I found out, in my case, there is an issue with Microsoft and the validation of the compliant devices.

I have Conditional Access and in one rule I have to validate the following(conditions):

• Mobile apps and desktop apps (this is the issue)
• Clients with inherited auth
• Clients with exchange
• other And it will check(grant):
• Compatible device
• Joined in Entra hybrid

But in my case, the user had the compliant device & Entra hybrid (I have it next to me and in Intune all checks are green), also on:

Entra > User > Devices

it shows they are Enabled, MDM, and Compatible. But the logs of the login attempts say it doesn't have it (Microsoft issue)

SOLUTION (Temporary):

I had to create an exception group for the user while Microsoft fixed this and added it to the conditional access. (Pls Ms fix this)

Also to notice the logs from the user came from a different location even when I had no VPN or anything going on. 3 devices on the same network and all came with different places FR, NL, [Current country]

Try to log in and it's done, and it came from the [Current country].

I hope this helps.

Please feel free to contact me for any updates. And if this helps, don't forget to mark it as an answer.

Answer 3

There were some previous positive reports indicating that clearing macOS Keychain helps. No need to wipe the whole Keychain (as it most likely contains useful authentication data for other applications that work).

In my case the following procedure was sufficient to resolve error 9n155:

1. Determine the Microsoft Entra User ID for the user that is getting error 9n155. User IDs are in GUID format.
2. Open macOS Keychain Access on the affected computer.
3. Search for the User ID (string in GUID format)
4. Delete all matching entries (they will have Kind == "application password" and Keychain will be == "iCloud" and "login")
5. Try logging in again in the application that was affected.