The [find familiar](https://www.dndbeyond.com/spells/find-familiar) spell declares a 100 foot distance for eligibility to deliver a spell with range of touch, but I do not see a distance listed for an attack delivered as a reaction of the familiar when the warlock takes the Attack action. So, does that mean they can deliver an attack from any distance if you have the Voice of the Chain Master invocation, which allows communication across any distance, and that it would probably not be allowed if you don't have that invocation?