Could Not Authenticate to SharePoint Online Using OAuth 2.0

Having some authentication issues?

In this guide, let’s discuss the authentication issues with SharePoint Online using OAuth 2.0.

Let’s get started.

Incorrect SharePoint Admin URL

Sometimes, authentication fails because the wrong URL is used during setup.

It’s common to mistakenly use a site collection URL instead of the admin center URL, as they’re similar.

For example, the main site collection URL looks like this:

https://yourdomain.sharepoint.com.

On the other hand, the admin URL looks like this:

https://yourdomain-admin.sharepoint.com

As you can see, the difference is the -admin part, which can be easily overlooked.

If you put the main site collection URL instead, it won’t work since the correct admin URL is needed for proper connection.

Related: How to Access SharePoint Online: URL and App Launcher Guide

Legacy Authentication Restrictions

Legacy authentication protocols can block successful connections to SharePoint Online.

These older methods are often disabled to improve security, but this can lead to authentication failures.

For this, you can use the -ModernAuth parameter with the Connect-SPOService cmdlet:

# Import the SharePoint Online Management Shell module
Import-Module Microsoft.Online.SharePoint.PowerShell -ErrorAction Stop

# Define the SharePoint Online Admin Center URL
$AdminCenterUrl = "https://yourdomain-admin.sharepoint.com"

# Connect to SharePoint Online with modern authentication
Connect-SPOService -Url $AdminCenterUrl -ModernAuth

Then, make sure that PowerShell scripts align with modern authentication standards.

You also need to confirm that your organization hasn’t disabled protocols necessary for modern connections.

Multi-Factor Authentication (MFA) Challenges

MFA can create hurdles when trying to authenticate to SharePoint Online.

While it strengthens security, it may conflict with traditional authentication methods.

This can happen when you use Windows PowerShell, and to fix that, just import the SharePoint PowerShell module:

Import-Module Microsoft.Online.SharePoint.PowerShell -UseWindowsPowerShell

Aside from that:

• Use the latest management shell
• Check authentication methods
• Use app passwords

MFA requires tools and scripts to support modern protocols fully.

I also wrote a separate guide on connecting to SharePoint using PowerShell with MFA, check that out if you need to.

Related: How to Connect to SharePoint Online Using PowerShell With MFA

Do you have any questions about authentication issues using OAuth 2.0? Let me know below.

For any business-related queries or concerns, contact me through the contact form. I always reply.

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