Doesn't your contract state something like "The cost of unforeseen events encountered due to the construction and installation
of this contract in reference to said project as bid that arise in the course of construction, that are beyond the scope of this bid but must
be covered within initial contract as a means to completion of said project are to be sent to owner or their representative for .... "
If I've learned anything in this work, "if you touch it one own it"! Now I'm not making a open statement that you now owe the panel.
But how can you install your work without a proper GEC to begin with?
Whoever inspected the job missed this fact!