Recently I have had a couple of situations where a server had been setup with remote access, but something changed and the remote access wasn’t working any longer or I couldn’t get it to work again. The first case involved changing out a DSL router at an office. Up until then the remote access worked fine. We configured the new router for remote access. but couldn’t get it working. The second case involved setting up remote access at a new office; the server had previously been setup in a different location. The same thing happened; remote access should have worked after setting changes on the router, but didn’t.
In both cases the problem was with how Windows handles new networks. By default on these servers, Windows saw the new router as a new network and the server move to another office as a new network (which actually was the case). In these situations Windows treats the new network as a public network. Typically office networks will be private networks. In Windows Firewall, there are separate settings for letting applications through private or public networks.
Because I had allowed the applications through a private network but not a public network I could not make remote access work. I had to change the way Windows viewed the network back to private. This can be done in the Control Panel, All Control Panel Items, Network and Sharing Center. Under “View Your Active Networks” you will probably see just one network, but underneath it will say “Public Network.” Click on that name (it should be in blue as a link). That will open a new window “Set a Network Location.” Click either Home network or Work network then click close. Now any Firewall rules that apply to private networks will work again. This solved both of my problems.