After updating the Endpoint Security System policy with incorrect proxy credentials, client(s) are offline and unable to communicate with the cloud portal.
This issue is caused by entering incorrect username and password credentials into the HTTP or HTTPS Proxy Configuration.
Edit the System policy where the incorrect credentials were entered and input valid credentials. After saving the policy create a new installation package. This new installation package will contain the updated proxy settings. Then this installation package can be run on affected clients to allow them to connect to the cloud portal.