Reading further on the page showed me this warning:
I set up my HDA with the defaults, so my IP was 192.168.1.10. I needed to change to something else, like 192.168.10.10.Make sure your HDA's network IP range is different than that of the remote network. (e.g. if your HDA's IP address is 192.168.1.X, you cannot connect to it on a remote network also using 192.168.1.X)
However, there's no good way to change the ip address / subnet for my hda. I ran hda-change-gw as suggested this this thread and I also changed my router's ip address, but the amahi control panel still thought that my network was located at 192.168.1.* and the OpenVPN connection logs suggested that it was still trying to connect to 192.168.1.*. Even though my internal network worked perfectly, I couldn't connect from outside the LAN. Is there a way to change hda-change-gw so that it updates the control panel about my network? Would that make a difference?
If that's not possible, there should at least be a warning when you set up your HDA for the first time that the user should not use a common subnet like 10.10.10.* or 192.168.1.*. That would help some of us avoid the pain of trying to change subnets later on.
I wouldn't mind writing up a bug about this problem, but I figured I should at least check if it even is a bug first.