Radar communication error

[Mr O]

I’ve got a 20 year old Simrad CA40 plotter and radar that are not getting along. I gave up on the radar over a year ago but decided to give it another try. After a reset on the plotter, i then input the radar model number and the radar fired up! Yesterday I went to the boat to test the radar again and I kept getting a splash screen the said theres a communication error. So I checked the wire connector, which looked fine and was firmly plugged in and then removed the radome cover to see if there was any corroded terminals. It was very clean and no sign of any problem. What is causing this sporadic failure? A software setting? Wiring issue? Is there a way to track this down?

Thx for any helpful suggestions.