Or HaChaim on Exodus 11:10/אור החיים על שמות י״א:י׳

1 ומשה ואהרון עשו…ויחזק ה׳ את לב פרעה, Moses and Aaron performed all these miracles in Pharaoh's presence….but G'd hardened the heart of Pharaoh, etc. This verse tells us that in spite of all the miracles Moses had performed, Pharaoh was still not willing to let the Israelites leave, not even conditionally, such as had been proposed in 5,3.