- WhatsApp was accessible, despite being expected to be blocked.
- Require to upgrade the Web Policy Builder to enable the Rule Tracing feature.
- Perform a rule trace, if the traffic flow was halted at the Hybrid Policy ruleset and did not proceed to the Global Blocklist rule and Hybrid Policy ruleset was configured to use the On-Prem Policy.
- Switching it to the Cloud Policy, then the access to WhatsApp will successfully blocked as intended.