Thanks Rodmuth! Though we got it to connect once by allowing this 'direct play helper' through the firewall by prompt, we're back to not being able to connect Darkest Hour via Radmin. Here's how I remember the solution we found, and it appears to have been caused by an AMD Adrenaline update on my windows 10 pc. Apparently playing DH requires a process 'dplaysvr' : direct play server or direct play 'helper'.
It's a legacy process, used only on older games. With a little more testing... Direct play is active now. If I can't connect now, I disable it, and try again. Perhaps that will activate the prompt. I have another problem now. Windows key no longer works to minimize. I'd like to fix that too. A restart has been recommended but I'm not really buying it. I know there are some people on the server more knowledgeable than I about connecting Darkest Hour via Radmin. I would greatly appreciate any tidbit of education on this issue, if not helping me test the solution.