P0671 = Cylinder #1 Glow Plug Circuit Failure
P0672 = Cylinder #2 Glow Plug Circuit Failure
.... and so on.
Last time I checked, a 6.0L diesel only has EIGHT cylinders.
Now, would be the time to do some datalogging of the usual 6.0L data readings that are immediately relevant to whether or not it will run, in order to pinpoint your issue, since no DTCs (or at least relevant ones) have set.
Ford Diesel/Senior/Master Tech
....who works at a dealership that now employs SOME half decent looking female employees since they overhauled most of the administrative staff
....and STILL hates working on E-Series with 6.0LFord Diesel/Senior/Master Tech