Hi @Eric Jones ,
Thanks for reaching out.
The error message "AADSTS90121: Invalid empty request" usually occurs when the SAML request is empty or incorrect required parameters.
Here the issue with the setup of the SAML application.
- Check the SAML request: Make sure that the SAML request is not empty and contains all the required parameters. You can use a Fiddler trace to capture the SAML request and check its contents.
- Check the SAML configuration: Verify that the SAML configuration in Azure AD matches the configuration in your SAML service provider. Make sure that the SAML endpoints, certificates, and other settings are correctly configured.
- Check the SAML service provider logs: Check the logs of your SAML service provider to see if there are any errors or warnings related to the SAML request. This can help you identify the root cause of the issue. I would suggest you take Fiddler trace to take capture the request and match the request which has to be an application side URL. Could you please check with the third-party application value to setup the proper request URL for the SAML SSO setup. Hope this will help. Thanks, Shweta
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