I’m quiet sure there is nothing wrong with your 688ci HD DI. I have one. The built in map provided by Humminbird is very limited as to bodies of water and details shown. When it looks like you are running over land this means the body of water you are on is not on the map. I still use the feature as it leaves a tracking trail. You can mark spots and still return to them by following the track. If you want a better map you will need to purchase a chip like from Navonics, but make sure it’s compatable with the 688
The GPS does take several minutes to find the satellites before it will work.