On the chart screen? What fishfinder info do you expect to see on the chart screen?
Did you try switching to a sonar screen? Perhaps the sonar is 'paused'. Of course, if the unit was left on for an extended period after the boat was hauled, you could have thermal damage to the transducer.
But SO MANY different possibilities here, and insufficient info from OP.
If you're "..not a Garmin guy" then why do you have that equipment installed? i.e. either become familiar with your installed equipment, or switch to some you know, or stay far away from other boats and skinny water.