You'll find nothing in the manual about this.

The assumption is that you already know what you are doing in putting together and flying this plane.

Most RC'rs know that the antennas must be fully extended.

If you look at the front underside of the plane, you'll see a black plastic trim fairing.

This has a hole in it, and a flap towards the front.

Free the flap and lift it, and you'll find the antenna coiled inside the plane.

You must pass it through the hole and straight back, affix it to the fuselage with tape ( I prefer a small amount of hot glue as it will do less damage to the foam if I have to remove the antenna later ).

Until you do this, the reception range will be extremely short producing what you are seeing.

While you are at it don't forget to properly check, balance and break in the EDF.