When using the feature to Register Cloud SWG (WSS) and Edge SWG (ProxySG) in the current system, the only permitted username is sg-register.
The password for the service is generated as a token in the WSS portal. WSS uses this token to identify the appropriate Web Security Service account.
This article details the steps to configure Cloud SWG (WSS) and Edge SWG (ProxySG) integration.
Register proxy device to cloud method works with license type with fixed single serial number.
With ISG Proxy enterprise license, same serial number can be used to create multiple proxy applications.
Ref--https://techdocs.broadcom.com/us/en/symantec-security-software/web-and-network-security/integrated-secure-gateway/2-4/About-ISG/About-Licensing.html
As cloudSWG would not able recognize unique devices proxy forwarding method needs to used.
https://techdocs.broadcom.com/us/en/symantec-security-software/web-and-network-security/cloud-swg/help/conn-matrix/conn-about-proxyforward.html
This configuration takes place in two parts - Configure WSS to expect a connection from your ProxySG appliance(s) using a unique token, then configure your ProxySG appliance(s) to use that token.
Cloud SWG (WSS) Web Security Service Portal
ProxySG