Navnet vx2 and DFF3 troubleshooting

My Navnet vx2 with DFF3 suddenly lost it's ability to see the bottom. Is there a step by step troubleshooting guide that will help me pinpoint the problem?

When you run the sounder selftest in the menu, does the test run or flash back to the menu?
It is normally faster to call our tech support from the boat for a walk through in troubleshooting the problem. After 4 mins of everything being powered on; what is your sounder stby light doing? (Off, Solid, Flashing very fast, Flashing one sec on and one sec off)

Thanks, Johnny. I'll have to check this when I'm at my boat this weekend. What is the number that I should call at tech support?

Furuno USA tech support numbers are 410-479-4420 and 360-834-9300.