If you whitelist a site via the Winston dashboard, the change has the potential to take up to 5 minutes to be recognized while browsing. Whereas if you whitelist directly from the browser extension it will be more of an immediate change. If it takes longer than 5 minutes via the Winston dashboard, check to see if your router is caching DNS entries. If you need access to the site right away, you can temporarily whitelist it. You can also flush your router's DNS cache to speed up the process.

Note: It is recommended that you disable DNS on your router as Winston already contains a DNS server. This can free up resources on your router and make it and your entire network run a little faster by avoiding an unnecessary DNS lookup.