Chances are that Norton is blocking the transfer. Go into it's firewall settings and allow the IP address of each PC on the network.
If that dosn't work, let us know what error message you get when trying to share files.
What is ransomware and how do I protect my PC from WannaCry?
What I learned from my mentor, Oscar-winning VFX supervisor Phil Tippett
Siri vs Google Assistant
Synology invites you to visit them at Insomnia on 26th – 29th August. Book your tickets now and visit Synology.