Question about Goal Zero Nomad 200

The 200W are ideal values that cannot be achieved under normal conditions. The 150W mentioned here are fine.

This morning at 09:45 the Nomad 200 is supplying me with 7.6A and 16.52V on the input side of the charge controller - that is already 126W. The pure solar panel output should be measured on this input side. The 13.5V sounds like battery voltage.

Please note that another influencing factor is the charge controller or power station used. What is used?
A Victron Energy SmartSolar MPPT 75/10 allows a maximum charging current of 10 A, as does a Yeti 400 with Goal Zero Anderson Power Pole to 8mm adapter.

We never exceeded 150W with ours, regardless of the day and position.

Your question is specifically: "Why don't you get the maximum power from a solar panel when the sun is shining?"
Google AI says: "You don't always get the maximum output from a solar panel, even when the sun is shining, because the "Watt Peak" (Wp) value is determined under ideal laboratory conditions that don't exist in reality. The main factors that reduce performance include non-optimal orientation of the sun, overheating of the panels, soiling, the inevitable loss of efficiency over time (degradation) and the nature of the sky, which leads to different types of sunlight."
This is (for once) very true. I have tested a lot, at 650 m as well as at 2100 m above sea level. I have never achieved more than 179 W (cloudless sky) with the Goal Zero Nomad 200 when I wanted to charge my Goal Zero Yeti 1000X Power Station. But..., you have to constantly track the panel to the sun. At least I achieve more than the maximum 119 W that I get from my 220 V socket.

Try changing the angle of the panel to get closer to the peak power. If the sun is high, the panel must be positioned flatter, the angle of the bracket is then clearly too steep.