Norton for a long time used to show clients site as blacklisted, I registered for https://safeweb.norton.com/ and sent a review request........ days passed by with no reply.
Scanned site at sitecheck.sucuri.net which too showed clean but blacklisted at Norton.
Later found a quick solution on Norton forums :
Submit category change request with WebPulse:
Please enter a valid URL for the review process - > valid URL for review - https://ecoinsee.org/ > Filtering Service - select 'Norton Safe Web'- > Your suggested category - 'Select a Category'- > Comments - add 'Safe Web Orange Caution with 0 Threats'-