The test report from the GFI test should have as found, as left, and as tested settings. It may be that it was tested at INST and not returned to the as found setting. OR that it was never tested at all and they just pushed the test button.
Another possibility is the GFI CT, is it summation or zero sequence? Was the ground connection made on the source side of the neutral disconnect link?
I would recommend you have an indepenent 3rd party test company retest the GFI, if it passes, then you have some troubleshooting to do.
