The article prescribes various ways to troubleshoot the Norton Antivirus Error Code 8504.421 for the Norton antivirus software as given by expert's in the field.
All this reasons are caused by a third party or directly by your internet service provider. In these cases you should be patient and wait for the outage problem to be resolved. Outages problems may persist and are very irritating, however, try to be
Norton antivirus is one of the important components of Windows, it’s not that mac or Windows is very highly vulnerable to viruses, but the use for which a Windows computer or Mac PC is used.