Outlook 2016 doesn't accept password or app password

Go into airplane mode for a bit (or just disconnect network) then re-enable the network. May have to do it a few times. Seems like some of their servers are fixed and some aren't, and each time you connect you get a different random server.

Unfortunately i've still got the issue. Enabled 2 step authentication but when trying to add my account back to office 2016 professional i'm still unable to log in, with both app password or my regular password. Windows credentials pops up and keeps asking to reenter but no success nop matter how many times until i cancel at which point it fails.

I've managed to add the account back on outlook, credentials requested the password 5 times before finally syncing. I log in daily so will update if there's any further issues.

I've logged in this morning and the issue comes up again. Requesting a password to be able to sync.

Still not resolved. After successfully re-adding my account on the gmail app, I'm now being prompted to "enter credentials for <email address>"

Hi all,

The service team asked me to get the Outlook.com email address for those seeing the issue so they can check the backend to investigate what is causing the auth prompts. Thank you to those that responded. If they need more, I will post again 2/2/24.

I am a developer in the MS ecosystem. If you have an internal case opened, please send me the case number and I will try to add more data to the case

You can simply tell your developers that every single client have this issue - I can narrow it down to say even every Microsoft-developed own client is having this issue, so you can eliminate 3rd party clients caused the issue.

I tried IMAP and have the same issue but normally use EAS because of faster and better sync.

1. Work computer Win11 running "Microsoft 365" Outlook 2308
2. Personal computer at home (not near it right now) Win10 64bit running Office 2016 version of Outlook, fully updated
3. Phone 1 running Android 13 and Outlook for Android has the issue
4. Phone 1 running Android 13 and running Google GMail latest this issue
5. Phone 2 running iOS 15 and running Outlook for iOS has this issue
6. Phone 2 running iOS 15 and running Apple Mail client has this issue

All my clients are up to date but I am not on Inside track, so these daily drivers do not have pre-release build of your clients.

Issue started suddenly on the evening 1/23 Pacific time. I started a business trip morning of 1/24, so this was a huge issue for me. I initially thought it might be a T-Mobile issue since my phone and home internet are on T-Mobile 5G. As I went on with my travel, touching internet on the plane, then onto internet in other countries, hotels, coffee shops and my foreign office - all have different ISP providers. THEY ALL EXHIBIT THIS ISSUE. I have removed/re-added my account on my devices so many times that I lost count. I even went into Outlook Web's mobile setting to delete the provisioned phone just to make it cleaner. 2 days ago, there was notable improvement but not full fix, but then yesterday as been hairy all day.

I actually think this issue impacts business accounts as well:

1. Personal account - we can these constant prompt asking for credential that everyone is about.
2. Business account - no such prompt, but emails, contacts and calendar are not syncing. My coworker wasn't even aware of this issue until he missed meetings because the phone didn't sync new calendar invites. Then it was very obvious the phone clients were not getting data sync'ed. If the account is deleted and re-added, all the data will sync correctly.