You have been tasked with selecting a 3rd party IdP to allow logging into ChromeOS...

The error message "Unable to sign in to Google" in the context of 3rd party IdP login typically points towards an issue with the SAML (Security Assertion Markup Language) connection. SAML is the standard protocol used for authentication between ChromeOS devices and external identity providers.

Here's a breakdown of troubleshooting steps:

Verify SAML Compliance: The most critical step is to ensure that the 3rd party IdP is configured correctly to use SAML 2.0 and is adhering to the required SAML attributes and formatting.

Check IdP Configuration: Review the SAML configuration settings in both the Google Admin console (under Security > Set up single sign-on (SSO) with a third party IdP) and the 3rd party IdP's administration portal. Ensure that the entity IDs, SSO URLs, and certificate information match exactly.

Test SAML Connection: Use a SAML testing tool (e.g., SAML Tracer) to simulate the login process and inspect the SAML assertions. This can help pinpoint any errors or inconsistencies in the SAML response.

Google Admin Console Logs: Check the Google Admin console logs for any relevant error messages related to the SAML authentication process.

Contact IdP Support: If the issue persists, reach out to the support team of your 3rd party IdP for further assistance. They may have specific troubleshooting steps or logs to help diagnose the problem.