Nope. My server sits behind my router so I’ve never felt the need for a firewall. Windows Firewall is off and I have no form of antivirus installed on it.
I have Hamachi installed and running, I could try closing it down to see if that helps, but it’s never interfered with anything before.
Other than that, nothing I can think of. The SMB shares mount fine so I don’t think it’s any kind of communication error between the computers.