I'm usinbg WIndows 10 but I'm sure it similar. If using WIndows FIrewall, you need to set a rule/exception for Himachi. If using AVG (I am using Ultimate) here is my response to the AVG community:
I recently had this problem when I started using Himachi again with AVG Ultimate and found that you need to add a "packet rules" named Himachi, Action - Allow, Protocol - All (probably could limit to TCP or UDP but decided not to try), Direction - In/Out, Address - blank. This is to be set on all computers accessing the Himachi network. This is under AVG Menu> Settings> Components> Enhanced Firewall > Policies.
Himachi dedicates a specific IP address to each client so you can enter each client in the Address column but they would require multiple entries and I found it was not necessary. All my network settings are set to "Private."