"Access Denied. Unable to authenticate the user." error while logging in to the vCenter server

Products

• VMware vCenter Server

Issue/Introduction

After switching the identity provider to Entra ID, we encounter the error 'Access Denied. Unable to authenticate the user.' when attempting to log in using a standard browser window. However, login via incognito mode works successfully.

Cause

Since authentication with Entra ID functions normally in incognito/private mode, and also works in environments that do not contain old browser data, this makes it unlikely that the Entra ID integration or its settings are misconfigured. If there were an issue with identity provider settings, login would fail universally, regardless of browser state or mode. The evidence thus strongly points to a browser-specific problem, likely with cookies, cache, or local storage persisting outdated or conflicting authentication data.

Resolution

Perform the following steps :

- Clear the browser cache

- Attempt to log in from a machine that has not previously been used to access the vCenter Server.

- Install and use a different browser (e.g., Firefox, Chrome or Edge) to log in.