Fanuc has multiple "systems" for G code. The most common is System A but your control could be using System B or C.
Try G92 ... works the same as G50. If it works ... you could run into other G code issues and you should investigate Systems B and C ... they are listed in the manual.
Hope this helps.
G50 on the ^T and M was used for Work cordinate or Tool Geometric on a lathe if the Offsett screen dint have it
First line in lathe programs used to be
Goo G90 G50 T0101 X100.0 Z50.0
On New controls and some updated ones G50 was used for Spindle cap as in G50 S2000 for max Rpm at that position