I have been having this same issue. Fishing in 10-16 ft and no matter what setting i tried, included factory default, I was unable to see my jig. At the best i could see a faint blue line that would often disappear. Nothing i could confidently jig against. I replaced my transducer with a new one and there was no change. After reading this forum, I decided to update my Hummingbird Helix 7 Chirp Mega SI GPS G3n from software version 1.9 to 2.180. The only fix i noticed in the notes was “SONAR: Fixed an issue where the default frequency on the HELIX 7 CHIRP MEGA SI GPS G3N was set to 455 kHz.”
Cannot wait to test tomorrow. Truly hope this works. Thanks to everyone for the posts.