There can be multiple reasons why authentications to the SaaS applications fail.
Time Synchronization: Access Gateway for Cloud depends on timestamps to function correctly. Synchronize time between the VMware host, the appliance, and the workstations. Download the authentication or single sign-on logs. In the catalina.out file, search for the error clock skew.
SAML Authentications: Firefox contains a SAML debug add-on you can use to view the SAML authentication between Access Gateway for Cloud and the SaaS applications. Download the add-on SAML tracer to view the SAML request.