We were under the Law, but now we are under grace. We used to be under a system where we had to live up to a certain standard to qualify for God's blessings. Now we are in a relationship with God in which He has made us His children and has given us His kingdom. He has given us everything He has, through Christ.
The issue is that what He has given us is primarily spiritual. Everything that Jesus paid for in our atonement is in us right now, in spiritual seed form. As we exercise faith in Christ, we make room in our hearts and lives for our inheritance to manifest from spiritual seed form to something tangible or substantive in our lives.
Faith doesn't make God move or cause Him to give us things, faith hosts God's presence within our inner man and allows God's spiritual power of grace to build His character and promises into our lives.
God is not withholding anything from us, but what He has given us must be received by grace through faith.
So how do we access grace by faith and experience the power of grace in our lives?