You will need to login with an account that exists in UEM in order to switch the enrollment. I would follow this guide to setup SAML between Workspace ONE UEM and Google. https://darrylmiles.blog/2021/06/13/setting-up-single-sign-on-sso-to-workspace-one-uem-self-service-portal-ssp-and-admin-console/
Look in %programdata%\Airwatch\UnifiedAgent\Logs for the log details - the device enrollment log would be the most help. But you will need to get the account you want to switch the enrollment to into UEM.