Working for me now too.  The must have fixed whatever certificate issues they were having.
Installing Support Assist fails with this error message: "Installation cancelledWe encountered an unexpected error while installing SupporTAssist. This may be due to a lost internet connection."   The Windows event log says:"SupportAssistCertificateValidationFailed - 7 : Certificate validation failed for SupportAssist".   What can be done to further debug this?   System:Dell XPS 15 9560Windows 10
Support Assist installation fails: Certificate validation