With a 740S a few years ago, solution was send it back to Garmin
and for a flat fee, they send you another one.
Of if is like mine, it got worse not better, then suddenly was dead, back up your waypoints before you send it in, you will not be getting the same box back, but you will get a replacement fast.
After that I bought a back up plotter, I bought and installed a Raymarine
Dragonfly as I wanted the sonar it had to find dive spots.
This based on a different product of course, but call Garmin
on Mon. and ask their techs. They may have you reload software
etc. and it may work?
Sent from my iPad
Pro using Cruisers Sailing Forum