After January 2019, you are unable log into a Symantec Endpoint Protection Cloud (SEP Cloud) portal that has been configured to use Okta as a 3rd-party identity provider.
When you try to open the Integrated Cyber Defense Manager, Symantec Endpoint Protection (SEP) 15, or SEP Cloud from Okta, you get the error: "Could not sign in to your account."
Symantec implemented changes to its data centers. As a result, a new URL must be used for the default relay site in Okta.
Please refer to the following screenshot as an example of what the above solution would look like in Okta: