At first this question might seem silly or pointless. Just because God is omnipotent and omniscient, why shouldn't he be able to have a will? But the issue becomes a little clearer if you think about the fact that there are no possibilities except one for reality. Statistics becomes meaningless. If you asked God what your chances were of making a 3-pointer with a basketball, He'd laugh. If everything could only happen one way because God would make it that way and knows it, then He can only make it that way and is in a sense a slave to His own future decisions, which essentially come out of nowhere.

Think about the following:

1. God is omnipotent and omniscient
2. God wills the Earth to have only one Moon ever
3. The Earth can never have more than one Moon because nothing can contradict God
4. God cannot will anything but for there to be one Moon for Earth
5. God has no will but must follow a certain course for the Moon to Earth ratio (1:1)

At first this problem seems a lot like the semantics of "Can God make a rock so heavy not even He can lift?" But it's different because instead of simultaneous power, the issue here is one of time and will, neither of which are subjected to omnipotence. So one cannot claim that this is an issue of semantics, because it is true that God cannot will otherwise in this scenario.

Of course, the full understanding is that God cannot will something against Himself, which again might seem like the problem misunderstands God's power, but that's not the case. The issue can be rephrased as: can God start making blue sweaters, one after another, every second? Yes. Can God switch to making red sweaters after X amount of blue sweaters? Yes. Then God can stop Himself from making blue sweaters and God can override His omnipotence.

This problem is not solved by the fact that God can have planned to stop making blue sweaters after X amount, meaning He was not employing omnipotence, because we can then ask: Can God make blue sweaters until someone (e.g. an angel) asks him to switch to red? If we try to say that God knows the mind of the angels, then let's suppose the following:

1. God places a force that prevents any sweater from being made unless He uses omnipotence to create it.
2. He therefore uses omnipotence every time He makes each blue sweater
3. To switch from making blue sweaters, He must check His omnipotence
4. Omnipotence cannot be stopped
5. God cannot switch to making red sweaters or stop making blue ones at all. He must open a different factory

But the issue with this thought experiment is that it goes in the same pitfall as "Is God more powerful than Himself?" The example sneakily places a limit on God that He places on Himself and then asks that He break it.

In other words, why is God supposed to on the one hand make a force that stops Him from making blue sweaters unless He uses omnipotence, and on the other somehow switch to red? It's illogical. If, on the other hand, we say that this is some natural force that God created and not His own direct power, then the way God starts making red sweaters is simply by eliminating this force and then halting the blue sweater-making process. The problem with the example is that it limits omnipotence to making blue sweaters and then asks how it's possible to stop making them: of course it wouldn't be. But God would not be using omnipotence if He planned on stopping the blue sweater creation. This, He must know in advance, which is why omniscience is in a sense needed for omnipotence.

So God can stop the blue sweater-making process because He never opted to use omnipotence on it: yet no other force can stop Him because He can always be more powerful than it. This is just like Cantor's explanation with Set Theory about how a finite distance can have an infinite amount of mid-points and there be different finite distances. In fact, to say that God would be using full omnipotence on making blue sweaters implies there is something omnipotent about making blue sweaters!

The problem is that if God is not using full omnipotence, then there is some Force A which can stop Him. On the other hand, if He is, then He can never switch to red sweaters. This is why Cantor's Set Theory is important in understanding how God can "stop Himself" from making blue sweaters if He wished.

Will is not a Predicate

But back to the original issue. To try and solve this by saying willpower is just a word for God's decisions and is not actually a "thin" doesn't help. The problem still stands: God can't do anything that was never part of His plan. Which means in a way the future stops Him.

Causality and Space-Time

The whole issue revolves around an incorrect point of view. From our point of view, yes, God has no way than to do as He planned. This is why God's promise would be unbreakable and He cannot lie (Hebrews 6:16-20). But from the point of view of space and time, this is an impossibility only if we give space and time the ultimate power, by looking at things from that point of view as an unshakable base.

If we look at things without causality, then we resolve the problem of how God can have an unchangeable will and for it to be a will at the same time since no other potential worlds are possible. Think about a simple mathematical truth like 2+2=4. You have to perform the addition of the two 2's to get the 4, but 2+2 always equaled 4 before all time. If you compare that to a math example where time does matter, such as the Monty Hall Problem, you see the values change: although there's two doors, one has 1/3 vs 2/3 chance, even though the prize never moved, and all you did was perform an irrelevant to the position of the prize action!

This way, if we understand that God made this decision while, if that word has any meaning, He executed that decision, we can understand that God not having a will because He couldn't change it has nothing to do with omnipotence, omniscience, or will-power, because time is not a factor to create any difference. It would be like saying I'm a different person than the "me" 5 minutes ago, which one can look at in a psychological way (e.g. I've learned something), but this would not apply in any meaningful sense if I removed time, any more than saying I'm a different person because I moved 2 feet to the left, even though one can legitimately try to say something along those lines (or say, Theseus' Ship Dilemma).

Otherwise, if you think about it, it implies that the universe/reality isn't random in its origin (that is its laws, its properties like how much energy and matter it has, etc), which it must be if we assume an atheistic approach. Because then you would say "the universe's past couldn't have been anything else," and not only does that mean that something random (with respect to patterns) is non-random (deterministic), but you would have to assume that genuinely stochastic (random) models of Quantum Mechanics are not simply untrue, but impossible - which no physicist considers.