Remove the blue probe (CH4 probe), select the 4th channel (press the CH4 button so it lights green), then press the "POSITION" knob (the one you normally turn). The blue trace should come to middle. (Yours will probably not come to middle, since in the pics it looks like you are probing a voltage > 40V).
The only other thing to try is to remove all probes, let the instrument powered on for 30 minutes (to achieve thermal equilibrium), then do a self calibration: Press "Utility" button, "down arrow" on the right side of the screen, then press "Self-Cal" button.
The self calibration routine will take a few minutes to finish.
From the pics, it looks like all this will be for nothing, most probably CH4 is defective.