Authentication fails on web portal with Azure Open ID (4380162)

Authentication to the One Identity Manager Web Portal using Azure OpenID (OAuth2) fails after redirect from the Azure login page. 

An error occurred while processing the request: POST https://<server>/apiserver/imx/login/portal 
System.Exception: An error occurred while processing the request: POST https://<server>/apiserver/imx/login/portal 
---> VI.Base.ViException: The user could not be authenticated. 
---> QER.OAuthAuthentifier.OAuth2Exception: An error occurred while sending the request. 
---> System.Net.Http.HttpRequestException: An error occurred while sending the request. 
---> System.Net.WebException: The underlying connection was closed: Could not establish trust relationship for the SSL/TLS secure channel. 
---> System.Security.Authentication.AuthenticationException: The remote certificate is invalid according to the validation procedure.

The API Server makes an outbound HTTPS request to login.microsoftonline.com to exchange the OAuth authorization code for an access token.

• The API server did not have Internet access, so Windows could not automatically download the intermediate certificate during TLS validation.

• This caused the TLS handshake to fail, resulting in the authentication error.

Ensure the certificates for Azure were installed on the APIServer - so the trust relationship was made.

https://learn.microsoft.com/en-us/azure/security/fundamentals/azure-ca-details?tabs=root-and-subordinate-cas-list