Welcome Martin t 101welcomw I'm not familiar with Hummingbird products but is your transducer at the correct angle whenever you switch back and forth? Older finders have a setting for arches or fish symbols that identify fish. Fish symbol selection is not advise as a submerged stick will show up as a fish symbol. Sensitivity level may need adjusted as well as ping speed. Have had a transducer to go out on me before only picking up depth signal but no fish arches. Transducer replacement was only option but that did fix that issue.