4kw Open Array not connecting

[JVM225]

The were fully charged and the boat was connected to shore power when I tried to get the radar to connect.
As the boat is new to me, I haven't torn in to it enough to find the dedicated source of power for the radar, or a switch to switch that circuit off.
There is a fuse for "radar" in the electronics fuse panel under the dash, but I'm not convinced that it is providing power to this radar unit which was a replacement for the one Sea Ray installed back in 2002. I've tested that fuse and it is good.
But I did power everything down, including the MFD's, turned off the battery solenoids, and shut down the AC convertor for a few minutes in an attempt to cut all power to the radar unit and reset it. Then I turned the convertor and battery solenoids back on, restarted one of the C125 MFD's, and again attempted to get the radar going but got the exact same results.
What can I try next?
Would it be worth powering up the MFD, and with it powered up, turning the power toggle switch on the base of the radar unit itself off for a minute or so and then back on again and then try connecting through the MFD again?
Does that toggle switch completely shut off power to the unit?
Thanks!