The 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?
There is no general distance limit on the familiar's actions
The find familiar spell imposes a distance limit on two things: communicating telepathically and delivering a touch spell you cast:
While your familiar is within 100 feet of you, you can communicate with it telepathically. Additionally, as an action, you can see through your familiar's eyes and hear what it hears until the start of your next turn,
Finally, when you cast a spell with a range of touch, your familiar can deliver the spell as if it had cast the spell. Your familiar must be within 100 feet of you, and it must use its reaction to deliver the spell when you cast it
Making an attack is not one of these two things, so it is not limited by them.
The Pact of the Chain feature that allows you to have your familiar attack as part of your Attack action says:
Additionally, when you take the Attack action, you can forgo one of your own attacks to allow your familiar to make one attack with its reaction.
It gives no limit on how far the familiar can be from you for using the feature, and does not even require that you communicate with the familiar to do so. If you needed to be able to communicate with the familiar to use it, it would say so. There are no secret rules, and there is no limitation on the distance for this attack.
Find Familiar (without Warlock-specific rules) says:
A familiar can't attack, but it can take other actions as normal.
While your familiar is within 100 feet of you, you can communicate with it telepathically.
...when you cast a spell with a range of touch, your familiar can deliver the spell as if it had cast the spell. Your familiar must be within 100 feet of you, and it must use its reaction to deliver the spell when you cast it.
These rules apply to Warlocks unless another rule overrides them.
Pact of the Chain says:
...when you take the Attack action, you can forgo one of your own attacks to allow your familiar to make one attack with its reaction.
No range is given, but it would be a reasonable assumption that you need to be able to communicate with them, to tell them to attack. Since Pact of the Chain doesn't change the general rules for communicating with your familiar, that would be 100 feet.
You can communicate telepathically with your familiar ... as long as you are on the same plane of existence.
Taking the same assumption as before, you can now tell your familiar to attack from anywhere on the same plane.