Yup, tried with a solid wire jumper, not stranded wire. Also tried with the cover breaker entirely off, no matter what it still has the dreaded "C"There’s no basis for that hypothesis.
They have no reason to think that they know which wires go to the green terminal block.
In any case, it seems that it should have worked with a jumper.
For the jumper, did you strip the ends of the wire to ensure good contact.
Did you also try it with nothing connected to the green terminal block?