have never seen the green LED on once.Gilles,
That is with the all QLG1s just powered up? I mean not connected to the U3S? Once locked the LED should flash.
If you have never tested them without connecting to the U3S I suspect a fault on the U3S causes this problem.
If you have tested them on their own then it looks like something you have done. But it seems unlikely you made the same error 3 times.
If the PPS input to the U3S is grounded by a solder splash or unetched track then maybe that is the problem. I'm not sure but some have had IC1 fail, maybe because of this.
73 Alan G4ZFQ