If you try to install an OPK, and then on your Zero open DinguxCmdr and navigate /media/data/apps. Do you see the OPK you tried to install? Does it have a size greater than zero? I don't know why this wouldn't work.
Or are you out of space on the Zero?
When it comes to actually connecting to your console, I would recommend trying to connect with an FTP program. GCW Zero Manager uses FTP to do the initial connection and install your public key on the device. If it doesn't work with another FTP program either, I can probably not offer much help, and it's better to ask the OpenDingux developers.