Certificate error attempting to access a CASB gatelet.
SSL_SG1-GLOBAL is a root certificate for Cloud SWG (WSS).
NET::ERR_CERT_AUTHORITY_INVALID or SEC_ERROR_UNKNOWN_ISSUER.
Verify the WSS Root Cert in installed in the workstation by using Windows certificate manager certmgr.msc
See CloudSWG documentation for more detail.
The workstation browser accessing the gatelet URL's that require TLS/SSL interception must trust the entire certificate chain.