Quotewith the multimeter leads on 20ASo you expect to see 6mA on a 20A full scale meter? How many digits does it have.Put the range down to 200mA and then you stand a chance.
with the multimeter leads on 20A
(and also tried the "plug" where it reads "mA"
you might have blown the fuse in your multimeter. The current input is often fused to protect the circuits but they do blow easily.