Password Manager - HTTP Error 503. The service is unavailable. (4381643)

After a change on the service account credentials (Password Reset/Change), Password Manager may report an error " HTTP Error 503. The service is unavailable." when trying to access the PMAdmin site.

The IIS Application Pool and site for Password Manager are configured to run under a custom domain service account.
If the password for this account changed or expired and IIS is still using the old credentials, the application pool will not start properly and IIS returns an HTTP 503 error.

The issue is resolved by updating the service account credentials in IIS:

• The Application Pool (PMAdmin) identity password must be re-entered.
• The PMAdmin site’s Anonymous Authentication must be configured with the same updated service account credentials.

After updating the credentials in both locations, the application pool can start successfully and the Password Manager site becomes accessible again.