Are you sure it's fret buzz and not the new bridge buzzing somewhere? The pups should hear fret buzz.
If the action is relatively high and your getting buzzing, it's usually one of two things...
1. Too much relief in the neck (forward bow in the neck) and the rod needs to be tightened maybe a quarter or half turn to pull the neck back a touch straighter. What happens is when you fret at the 5th to about the 12th, the string will rattle against the last few frets.
2. or it's somewhere in the bridge, springs, whammy; somewhere else in the system.
If you recently went to a heavier gauge string without tightening the rod a touch to balance out the increased forward bowing tension, excess relief could be it. Sometimes weather/humidity changes will cause that too. I just had to tighten the rods on a few guitar because of the recent weather change.
Since the pups aren't hearing it, not fret buzz would be my best guess, but it's tricky because sometimes the pups won't hear certain kinds of fret buzz either.
If it's only the low E buzzing, and only the open string, the nut slot is cut too deep and it's buzzing on the first fret. But that would have been an issue before the bridge change.
Tough to say without seeing it, but there's a few ideas that could get you on a path to solution.