Pharaoh sent officials and found that none of the livestock of the Israelites had died. But Pharaoh’s heart was hardened, and he would not let the people go.
Jewish Publication Society of America Version (JPS1917) - Exodus 9:7 >And Pharaoh sent, and, behold, there was not so much as one of the cattle of the Israelites dead. But the heart of Pharaoh was stubborn, and he did not let the people go.