If you have another PC on the network, you can try connecting via the sharing. Otherwise the most likely cause is the firewall.  There's no need to open a port on the router unless you want to access the collection over the Internet.  Temporarily disabling or even uninstalling the firewall may resolve it.  After resolution, re-enable or re-install and open the port again.

The other option of course is to sync via DPO upload/download.