Does God withhold blessings and communications? I don't know the theology requisite to a response to this question. I do know that over the years I have heard people, dear saints of The Kingdom, say that it seemed God did not hear their prayers; that the ceiling above them was of brass and their petitions would not penetrate it. Just this past week as I attempted to exchange words of consolation to a newly widowed friend she responded with, "God did not answer my prayers."
A difficult moment in the lives of two Christians as they converse at the foot of the casket of the dear departed spouse, the one wracked with grief and doubt, the other feeling failure in his role as comforter. We know that God does all things well and in His wisdom chooses the timing of His blessings. We know this, and we know that it is ours to accept God at His word, to await His time. And yet.
We read in Isaiah 54:8 "In a little wrath I hid my face from thee for a moment; but with everlasting kindness will I have mercy on thee, saith the Lord thy Redeemer." (KJV)
Doubt is not sin; we are human. Yet He will hold us in His hand in spite of our own tenuous grip.
btw, I have heard it said that doubt is the opposite of faith. No. In fact, doubt may be the foundation of faith, for without questioning there is no basis for believing. Or so I think.
I pray as the father of the stricken son in Mark chapter nine, " Lord, I believe; help thou mine unbelief."