Exodus 9:7 And Pharaoh sent, and, behold, there was not one of the cattle of the Israelites dead. And the heart of Pharaoh was hardened, and he did not let the people go.
God was showing His power by judging Egypt. When the cattle of Pharaoh die and none of the cattle of the Israelites die then Pharaoh is hardened again. I can imagine how he must have felt. He was angry and wanted vengeance. He couldn’t let God kill his cattle and do his people harm.
He would have to admit that God was God. That was too much. He could see His power but His pride kept him from believing God. That is the condition of man.
He may even see that God is powerful and obviously God but refuses to admit that. He will not accept that God can be all powerful.
Sometimes getting God’s judgment is only going to harden the person. That is not God’s design necessarily but rather the fact that people hate to imagine that someone has that much power over them.