Unable to log into vCenter using Active Directory domain account / Backups started failing with Invalid AD credentials errors

Products

• VMware vCenter Server

Issue/Introduction

Logging into vCenter with AD credentials had been working, then suddenly stopped working. Backup systems relying on AD credentials to authenticate with VC stop working.

• Applies to any AD domain SSO IdP configuration.

Cause

The required AD Identity Source was removed somehow from vCenter.

Resolution

Review the vCenter's current SSO Identity Source configuration to confirm if the required AD domain IdP is missing (Menu > Administration > Single Sign On > Configuration). If it is missing, AD users will not be able to authenticate when trying to log into the VC.

• Follow steps from "Add or Edit a vCenter Single Sign-On Identity Source" to re-add the necessary IdP for the AD domain.
• Test to confirm users are again able to log into vCenter using their AD credentials.