A while back my 2018 force 400 started to read the fuel level incorrectly. Eventually it started reading empty always. An earlier search on this forum lead me to think it was the fuel level sensor. I replaced that today but it's still reading empty while the tank is full. I tested  the new sensor and the level on the dash changes as I move the float arm up and down.

Any ideas on what I can check? 

[2015 Z Force 800 53/Trail EPS]

You are saying it works manually working it outside the tank but it acts like the float isn't floating when in the tank. Can the arm be stuck-down for some reason? Can the float...not float? Can there be a connection problem like a failed connector or ground?  What does the old one do out of the tank? 

Yes, when i moved the fuel level sensor arm before I put it in the tank and while it was connected electrically, the fuel gouge was going up and down.  Tomorrow, I will see if I can get to the arm while its in the tank and try again.  I hope that I can reach it with a wire or something.