When you say that the Grip Safety doesn't work, exactly what isn't working?
Is it not blocking the trigger from moving to the rear? Is it not disengaging afr enough, and allowing the trigger to move back?
If it is the first, the tang needs to be lengthened by careful peening, and re-filing, and if it's the second, then file slightly to provide clearance when the safety is depressed.
The new parts could be slightly off from what was installed, or it may be assembled incorrectly, though not likely.
More description would help.