Coderless operation on this control is an option that must be
purchased either from Fanuc America or GEFanuc. However, you might try
converting your IPR moves to IPM to get by until you can get the
encoder fixed. Make sure that all axis moves are either G00 moves or
G94 moves. You won't be able to thread or do CSS, but you might be
able to get your part out.
By the way, most spindle encoder problems turn out to be related to
the encoder belt - have you checked it?