Well I was Stanford on Platonism and they mentioned that abstract objects are acasual and do not have causal relationships to the world. Regarding what you said about classical ontology does God also act in a paradigmatic way as He is immaterial like abstract objects.

In classical ontology the forms are also likely immaterial concretes, though I'm not sure why we would admit of the class of immaterials that don't do anything. I suspect that the category is a confusion of intellect and imagination.

If there can exist immaterial concrete objects then how come in modern day platonism they are immaterial but abstract and thus acasual. I'm primarily focused on platonism because for me people like Frege have shown that philosophy can tell us that the immaterial exist such as in the form of abstract objects, and if this is established then for I think that philosophy can also tell about the existence of other immaterial things such as God, but the abstract/concrete immaterial distinction is something I'm having trouble understanding as at what point does philosophy tell that this immaterial object is abstract/concrete?

AKG wrote:

...I'm having trouble understanding as at what point does philosophy tell that this immaterial object is abstract/concrete?

By 'this' do you mean God or any immaterial object? You can reflect on when and why it became clear to you that something was immaterial. From your posts it is clear you accept some immaterial things.

Regarding causality, consider that you can know something required a cause even if you do not know what the cause is. If there are things in the world that require a cause or causes the nature of which cannot be material, then you have reason to suspect an immaterial cause for those effects. Regarding how the immaterial or the abstract can be causal, the objects of desire are traditionally given. Often such things may not even exist yet but that does not prevent you from pursuing them.