Seeing many things, but thou observest not; opening the ears, but he heareth not.
Seeing many things, but thou observest not - thou dost not keep them. The "many things" - are the many proofs which all along, from the first, God had given Israel of His goodness and His power, (Deuteronomy 4:32-38; Deuteronomy 29:2-4; Psalms 78:1; Psalms 105:1-45.)
Opening the ears, but he heareth not - transition from the second to the third person. "Opening the ears" -
i.e., though he (Israel) hath his ears open (note, Isaiah 6:10). This language, too (note, Isaiah 42:19), applies to Messiah as Yahweh's servant (Isaiah 50:5; Psalms 40:6).