Sorry, the authentication was not successful in Dynamics 365 App

"Sorry, the authentication was not successful" error occurs in Dynamics 365 App for Outlook

Applies to: Dynamics 365

Symptom

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When attempting to use the Dynamics 365 App for Outlook on Outlook desktop, you see the following error:

"Sorry, the authentication was not successful. We can help you fix the problem."

Cause

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Cause 1: This can occur if not all of the URLs used to authenticate and access Dynamics 365 are in the same Internet Explorer security zone.

NOTE: If you are using Dynamics 365 (online) with an Exchange Online mailbox, this is likely not the cause of the issue. 

Cause 2: This can occur if the LocalLow folder has an incorrect integrity level. The correct setting is to have the integrity level set to low as the folder name indicates.

Cause 3: If you click the option to show more and you see "Error: QuotaExceededError", this indicates your local browser storage limit has been met.

Cause 4: If you are accessing Outlook Web Access, this can occur if 3rd party cookies are blocked in your browser settings. 

Resolution

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Resolution 1:

Use the steps in the following article to verify each of the necessary URLs are in the same Internet Explorer security zone.

https://support.microsoft.com/help/4035750

Resolution 2:

1. Open a command prompt.

2. Run the following command:

icacls %userprofile%\Appdata\LocalLow /t /setintegritylevel (OI)(CI)L

Resolution 3:

Clear your browser cache

Platform	Instructions
Outlook (same as Internet Explorer)	View and delete your browsing history in Internet Explorer
Internet Explorer	View and delete your browsing history in Internet Explorer
Edge	View and delete browser history in Microsoft Edge
Chrome	Clear cache & cookies

IMPORTANT

Although you may have other browsers installed on your computer, Outlook desktop always uses Internet Explorer when displaying web content such as inside Dynamics 365 App for Outlook.

After clearing your browser cache, close all Internet Explorer and Outlook desktop windows and make sure through Task Manager there are no remaining Internet Explorer processes running.

If this issue only appears in Outlook desktop and clearing the cache via Internet Options does not help, try clearing it via F12 chooser (not applicable for Windows 7):

1.     Open Dynamics app in Outlook desktop

2.     Open IEChooser.exe in %WindowsFolder%\System32\F12 (example: C:\Windows\System32\F12)

3.     Click Dynamics 365

4.     Click the Network tab and then click the Clear cache button.

After following the steps above, reopen Outlook and the Dynamics 365 App for Outlook to see if the issue is resolved.

Resolution 4: If the issue occurs in Outlook Web Access, open the settings for your browser to verify a setting is not enabled to block third party cookies. 

NOTE: Some browsers allow you to block 3rd party cookies but add specific URLs to a list of allowed sites.