AKG wrote:

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?

Because immaterial concreta are by definition particulars (as opposed to universals). It would be more helpful for you to look at the abstract/concrete divide in terms of universals, with abstracta being one variant on the transcendent universal.

As to the last question ('at what point does philosophy tell that this immaterial object is abstract/concrete?') it depends on the proofs for said entity e.g. cosmological arguments point to a being which is not material and posses casual powers (what is omnipotence if not possession of casual powers) ergo said being is concrete. Likewise for proofs of the Mind's immateriality.