Just a thought, if you are using the demo version there is a 20 device limit, Have you reached that? the Pro symbol next to the devices suggests that.
As far as I understand it, and I'm no expert here, the comms is only one way with this type of device, that is for a temperature device the device will send data to indigo, but you can't interrogate the device and get a response. Similarly with a remote control, Indigo can duplicate the remote and send off/on/dim instructions and the device will respond to those, what you are seeing in the status is the last sent command from Indigo.
Normally to install a plugin all you have to do is download the plugin from wherever and double click on it to install or upgrade/downgrade.
Colin