Your site opens perfectly on your laptop. Your customers keep sending you screenshots of a block page. Nobody is imagining anything - the warning only exists inside certain products and certain networks.
This is the most confusing version of the problem, because the site owner is the one person who cannot see it. There is no banner on your server and nothing in your hosting panel. The block is generated on the visitor's machine, by the visitor's security software, using Norton's rating of your domain. Once you understand who carries that rating around, the mystery disappears - and so does the temptation to argue with the customer.
Norton's consumer products rate every site against Safe Web data and interrupt the ones rated badly. Office PCs running Symantec Endpoint Protection do the same with their reputation and intrusion-prevention features - that is the exact block shown in the video. No Norton or Symantec product on a machine means no Norton warning on that machine. That is the whole reason you and your developer see a healthy site while a customer sees a red page.
It is not only personal antivirus. Company proxies, school networks and some internet providers run security DNS and filtering services that block listed domains for every device on the network. A customer can be blocked at work, fine at home, and blocked again on a filtered public Wi-Fi - with the same phone. The common thread is never their device; it is your domain's rating meeting a filter.
Stop refreshing your own browser and gather the real evidence:
You cannot switch off other people's antivirus, and you should never want to. The only fix that reaches every visitor is changing the rating itself: run the false-positive checks, clean the site if anything is found, then file the Safe Web dispute so the domain is re-evaluated. While that runs, your other raters - Google Safe Browsing for Chrome users especially - deserve the same check, because a customer on Chrome may be hitting a completely different list.
A flagged site plus silence reads as a dead business. Post a short, honest notice where your customers already follow you - your social page or WhatsApp channel: some security software is showing a warning on the site, it is under review, and here is how to reach you meanwhile. Customers forgive a explained problem quickly. They do not come back to a site that simply stayed scary.
The video is filmed from exactly this side of the problem - a visitor hitting the Symantec block. Watch it and you will recognise your customer's screenshot instantly.
▶️ Watch Full VideoAlmost certainly not. Neither you nor your developer runs the product that produces the warning. The customer's security software is doing precisely what it is designed to do with your current rating.
Never. It is genuinely unsafe advice, it destroys trust in your business, and most office users could not do it even if they wanted to - their settings are locked by IT policy.
Only if Google Safe Browsing also lists you, which is a separate check in Search Console. A Norton-only flag does not change your Google rankings or your Chrome traffic.