Try the Restore Defaults choice under the Setup tab ...
Then power off and power back on ...
During boot up watch the screen for a popup that says "Transducer not connected" ...
If you don't get that popup ... The unit should boot up to the NAV disclaimer screen ...
Press the "Exit" button at the NAV disclaimer screen to start Normal operation ...
Test on the water ... (Sonar doesn't work thru air) ...
Rickie