why some poker players seem to never bluff successfully

noticed something in my last few sessions - some players just never seem to get their bluffs through, even when their lines make sense and the board looks good for it. i’m not talking total fish, either, but regulars who play solid otherwise. i’m trying to figure out if it’s something about how they bet or just the timing.

could it be sizing tells, table image, or maybe they give off some live “vibe” that screams bluff when they try it? anyone here ever fixed a similar leak in their game, or spotted one at your table? would love to hear how you picked up on it or adjusted for it.