I took a peek at one manual hoping the flashing zero would be in the troubleshooting section, but all I found was this (for the X96):
The water may be deeper than the sonar's ability to find the bottom.
If the sonar can't find the bottom signal while it's in the automatic
mode, the digital sonar display will flash continuously. It may change
the range to limits far greater than the water you are in. If this
happens, place the unit in the manual mode, then change the range to a
realistic one, (for example, 0-100 feet) and increase the sensitivity. As
you move into shallower water, a bottom signal should appear.
Transducer has to be submerged and angle set to get proper reading, try removing the connections and clean them with compressed air, the type for computer use. Mine the connection right at the transducer I have to fiddle with it to get it to work. (Real frustrating because there is no fix for that other than a new tranducer which is just as much as the whole unit)
