@sirrick
I have the same problem. I have disable my firewall in windows, open my ports in the router, a static IP4 address. But if I start my masternode is the same error displayed:
"Not capable masternode: Can't detect valid external address. Please consider using the externalip configuration option if problem persists. Make sure to use IPv4 address only."
I do not understand why it should be a security problem to run the MN on the desktop at home. if you rent a server the coins somewhere in the world on a computer, since can also happen a lot ...
Hi, I also tried to run a masternode. I installed Vivo (on Win), then I also got the error.
I added
externalip=x.y.z.a
to the vivo.conf file and then it worked, maybe this will help you too
But now I got a different problem:
Overnight my IP changed and I wanted to restart the masternode but I couldn't because of that. What I did is: I generated a new masternodekey, transfered the collateral to the new address and wanted to restart everything with the new IP, I even initialized all the *.dat files (apart from wallet.dat). But now I get either your error above or this when specifying the new IP using externalip: Not capable masternode: Mastenode not in masternode list. How to solve this? (Of course its not in the list, its a new one! but yeserday it worked

)
Hey, did you solve the problem? I have the same issue.