Web Isolation is blocking the domain being used even when the domain has been added as a Trusted Destination in the Web Security Service (WSS) portal.
Web Security Service
Web Isolation is set up with a policy to block and isolate suspicious websites. For example, a policy is set up to block domains with a risk classification rating of 5 - 10. The domain being accessed has a risk level of 10 and Web Isolation is isolating and blocking the domain. This will occur before the domain reaches WSS and, as a result, any of the rules listed under Trusted Destinations will not be applied.
In addition to adding a domain to Trusted Destinations, the domain needs to be added to a policy under Web Isolation that is set to "Do not Isolate". This rule will tell Web Isolation to not isolate or block the domain and, as a result, the domain will reach WSS and will be evaluated under the policies listed in its configuration, including the Trusted Destinations.
To create a rule to exempt a domain from Web Isolation:
From within the WSS portal: