Norton 360 error code 8504 is a technical error which occurs when users have another antivirus installed with Norton on their system and then you try to update it to the newer version of this security program. During the update of this antivirus, the installation will be unsuccessful and this error appears. This problem occurs when the files of this security program are infected by other software or due to the corrupted registry.
In order to fix this error code, Norton antivirus technical support here provided a few simple solutions. Just go through below given solution properly.
Re-Install The Program
Even after executing all the above steps, the error is still not fixed, then immediately call us at our Norton customer support number +1-855-2649-333 and get an alternate possible solution from our engineers.