Issue: You have added a entry like www.xyz.com to either the white or black list under Global Setting. For the whitelist you are still being blocked and expect to have access, for the blacklist you are being granted access and expect to be blocked.
Cause: DNS Caching is the likely cause for this and is not a specific Securly issue. It has to do with the way the DNS protocol works. DNS responses have a Time To Live (TTL) that could range from seconds to hours. What is likely happening here is the TTL on the DNS entry for the domain has not expired yet.
Solution: The issue will persist until the TTL on the DNS entry expires and the host makes a fresh DNS query. You may take the following steps to accelerate releasing the cache on the client of the affected machine.
Clear your DNS cache using the following commands:
Windows - command line: ipconfig /flushdns
MacOS - terminal: dscacheutil -flushcache
Before you expect to see results, make sure you run these commands on both the end host and the DNS forwarder. Also, close and restart your browser.