Contradiction with Jeremiah 31:33
This verse speaks of God putting His law in people's hearts and minds, implying understanding, whereas Isaiah 29:11 describes a prophecy that is unreadable like a sealed book.
Jeremiah 31:33: But this [shall be] the covenant that I will make with the house of Israel; After those days, saith the LORD, I will put my law in their inward parts, and write it in their hearts; and will be their God, and they shall be my people.
Contradiction with Ezekiel 36:26-27
God promises to give a new heart and spirit to understand His ways, which contrasts Isaiah 29:11's depiction of a closed revelation.
Ezekiel 36:26-27: A new heart also will I give you, and a new spirit will I put within you: and I will take away the stony heart out of your flesh, and I will give you an heart of flesh.
Contradiction with Matthew 11:25
Jesus thanks the Father for revealing truths to the simple, contradicting the obscurity in Isaiah 29:11.
Matthew 11:25: At that time Jesus answered and said, I thank thee, O Father, Lord of heaven and earth, because thou hast hid these things from the wise and prudent, and hast revealed them unto babes.
Contradiction with 1 Corinthians 2:10
Paul explains that God reveals mysteries to us by His Spirit, countering the notion of a sealed document in Isaiah 29:11.
1 Corinthians 2:10: But God hath revealed [them] unto us by his Spirit: for the Spirit searcheth all things, yea, the deep things of God.
Contradiction with 1 John 2:27
The anointing from God teaches believers all things, which juxtaposes the concealed nature of the prophecy in Isaiah 29:11.
1 John 2:27: But the anointing which ye have received of him abideth in you, and ye need not that any man teach you: but as the same anointing teacheth you of all things, and is truth, and is no lie, and even as it hath taught you, ye shall abide in him. [in him: or, in it]