DND_Reborn
The High Aldwin
Given the wording under the Help Action:I'd say having the familiar do a 'help' action would break invisibility and Sanctuary. I see it as the equivalent to an attack.
I would also rule this removed any Invisibility. If the target creature can't see you, how are you really distracting it???

But, since @TrueBagelMan doesn't feel that way... it is simply a difference in rulings. shrug
IME such foes are not commonplace at all. Sure, there are some, mostly in tier 3 and tier 4, though, but by then most familiars aren't of much use either.The invisible familiar dies easily against Truesight and Blindsenses. If they are on the ground then also tremorsense.