Generally, the Antivirus Providers blocks certain Sites (like Writer, etc.,) on their software according to their Clients request or complaints.

For example: 

1. Let's assume that you have installed an Antivirus Software (say McAfee) in your laptop.
   
2. If you receive any links from an anonymous user/service or if the content received is not relevant, you can go ahead and block such services/domains using your installed Antivirus Software.
   
3. If the Antivirus Providers receive more number of requests (asking to restrict any services/domains) from their Clients, they will go ahead and block them. 
   

Thus, if the users thinks that the file shared from our Writer service is not relevant/required for their workflow, they might have blocked our domain using their Antivirus Software. In order to unblock it, user needs to either contact their Antivirus Provider or write to us at: support@zohowriter.com. Please write to: support@eu.zohowriter.com if you're from EU region.