Traffic from Unmanaged SEP for Mac 14.2 client doesn't flow through the system proxy setting during liveupdate. As a result, definitions cannot be updated.
Known limitation. Proxy is not supported on 14.2 Unmanagaed Mac client.
Starting from 14.2, default liveupdate server is set to HTTPS server which is https://liveupdate.symantec.com and the HTTPS connection through HTTPS proxy is not supported currently.
Even though HTTP connection will be attempted after HTTPS connection failure, HTTP connection though HTTP proxy is not supported on 14.2 Unmanaged Mac client either. Only direct connection will happen to Symantec liveupdate server currently.
HTTP proxy for Unmanaged 14.2 Mac client and HTTPS proxy will be supported in future release. This article will be updated accordingly when further information available.
As a work around, bypass the traffic towards liveupdate.symantec.com so that direct connection to be used if possible, or use previous version of SEP for Mac prior to 14.2 instead which can connect to Symantec HTTP liveupdate server through HTTP proxy.