Outlook keeps asking for password

[Jeesoon]

Hi, we are having an issue with Outlook with an Office365 account on some user. the password prompt are keep on showing.

I tried running SARA, update windows 10 and office apps, create new profile, remove all credentials from credential manager, do the registry thing, disable antivirus but everything does not work.

[#2]

Just wanted to cast my vote as well that setting these three registry keys solved my same issue as well. Two weeks ago my desktop outlook started continuously asking for (and not remembering) my office 365 account password, would not download new data, and was not giving any kind of prompt as to what the error was, it just kept asking. After spending one or two hours here and there looking for and trying solutions, these registry key settings below (from the "best response on page two) fixed my problem.
Thank you!

HKEY_CURRENT_USER\Software\Microsoft\Exchange\AlwaysUseMSOAuthForAutoDiscover REG_DWORD 1
HKEY_CURRENT_USER\Software\Microsoft\Office\16.0\Common\Identity\EnableADAL REG_DWORD 1
HKEY_CURRENT_USER\Software\Microsoft\Office\16.0\Common\Identity\Version REG_DWORD 1

[#3]

@MathieuVandenHautte life-saver! I'd found this registry entry but the page I'd found said it had to be set to 0 not 1 - doh! Not sure WHY this key hasn't made it into some of my client's computers. Caused all sorts of hassle today as basic authentication was disabled.

[#4]

Microsoft disabled basic authentication for most tenants over the past few weeks. They have warned us about this for ages BUT have always said that Office had been updated to use modern authentication for years. So clearly we didn't worry about it. But this bug has caught many people out. There is an Azure report you can run to determine which uses are still using basic authentication with Outlook.

[#5]

@Jeesoon Hey there , I want to share with you the most stupid way ever to fix Outlook 365 (latest preview build of MAfB v2303) asking for password....

Today, all of a sudden, the prompt (Windows Security) popped out asking for password. I ticked remember, entered the password, clicked OK. It asked again for password... I entered again, then the Autodiscover (certificate window) appeared i clicked Yes... Spent the next 4h trying to fix, using regedit, all the possible tips & tricks to overcome the issue. Also created new Win user profile, in which it worked flawlessly... switch back to main user account, tried the store app Mail, it worked, no issues there... 

And as i was getting ready to give up... I remembered there is an option "Try the new Outlook" (top right corner under X to close Outlook 365 for Desktop)... I did, it downloaded new ver. asked me to Switch, so i clicked on it as well... Waited for it to import settings and preferences... and bam! no password prompt. 

Microsoft, seriously what the hell is going on? If anyone knows what does this have to do with anything please explain...

[#6]

@Antrophin3 Also in addition to that possible fix of trying the new outlook design... 
I have also applied the 3 .reg edits, switched back to standard Outlook, and voila... works again. Thanks so much for these @OP. 

Here is the code to make the .reg file (in Notepad). Just copy and paste it to new Notepad document, and save it as "LoginFix.reg" or however you wish... 

Windows Registry Editor Version 5.00

[HKEY_CURRENT_USER\Software\Microsoft\Exchange]
"AlwaysUseMSOAuthForAutoDiscover"=dword:00000001

[HKEY_CURRENT_USER\Software\Microsoft\Office\16.0\Common\Identity]
"EnableADAL"=dword:00000001

[HKEY_CURRENT_USER\Software\Microsoft\Office\16.0\Common\Identity]
"Version"=dword:00000001