If you’re unable to log into ExtendSync and receive the following error:

{

"error": {

"code": "CEFI-AUTHO-E1106",

"details": "Session details missing. Error Code: CEFI-AUTHO-E1106"

}

you’re encountering a session storage or authentication cache issue.

This typically occurs when session data becomes corrupted or outdated in the Outlook desktop environment.

You may still be able to log in successfully through Outlook on the web (outlook.office.com) because it uses a separate session store.

Symptoms

You can log in to ExtendSync via Outlook on the Web, but not via Outlook Desktop (Exchange).
Other users in your organization can connect without issue.
The error appears immediately after selecting your NetSuite (OneWorld) account connection.

Cause

The error CEFI-AUTHO-E1106: Session Details Missing occurs when:

Cached session details for ExtendSync in Outlook are corrupted or missing.
The local or Office WebView2 cache fails to pass valid authentication data to ExtendSync.

Resolutions

Try each of the troubleshooting options below in order.

Troubleshooting 1: Refresh the Outlook and Web Session

Completely close all Outlook windows.
Open Outlook on the Web at https://outlook.office.com.
Log in to CloudExtend there.
After successful login, restart the Outlook Desktop app.

💡 This step reinitializes the Microsoft session that ExtendSync uses for desktop authentication.

Troubleshooting 2: Clear Local Storage Data

Close Outlook completely.
Open Outlook again and open the ExtendSync add-in.
Right-click anywhere inside the add-in panel and select Inspect.
In the Developer Tools window:
- Go to the Application tab.
- Expand Local Storage, right-click your ExtendSync domain, and choose Clear.
- Expand Session Storage and do the same.
Press Ctrl + R (to reload the app).
Try logging in again.

💡 This clears outdated local session data that may prevent ExtendSync from establishing a new authentication token.

Troubleshooting 3: Clear the Office Add-In Cache Manually

Close Outlook completely (make sure no instances remain running).

Open File Explorer and go to:

%LOCALAPPDATA%\Microsoft\Office\16.0\Wef\

(Optional) Back up the folder contents.
Delete all files and subfolders inside the folder.

If this folder exists, clear it as well:

%userprofile%\AppData\Local\Packages\Microsoft.Win32WebViewHost_cw5n1h2txyewy\AC\#!123\INetCache\

Restart Outlook and try signing in again.

💡 This resets the WebView2 cache used by Outlook add-ins and resolves corrupted authentication data.

Additional Tips

Always make sure you’re using the latest version of Microsoft 365 and Outlook Desktop.
If the issue persists, disable and re-enable the ExtendSync add-in via:
File → Manage Add-ins → My Add-ins → ExtendSync → Remove / Re-add.
Verify that your Windows user account has sufficient permissions to modify the cache folders listed above.