Testing SP120 panels

I am reading 11 volts on my panels with full sun at 5pm. The spec is 20ish. What am I doing wrong. I have a fluke multimeter set to DC. Short circuit current is 4.5 A

It is hard to say without any detail of what you are doing.

Are the panels unfolded and pointing towards the sun?
Are the panels connected to anything?
If they are connected, what are the indicated watts that are being produced?

Voltage should be in the 16 to 18 range under full load.