hi! there's lots of room for a comprehensive overview on this topic, but meanwhile you may be interested in these posts
Did the Egyptians adopt aspects of Roman religion in the same way that the the Romans adopted some aspects of the Egyptian religion?
What happened to the ancient Egyption religion?
Why did Akhenaten decide to change Ancient Egyptian religion so much? <- follow the links
When the Hyksos held Egypt, was the egyptian religion dissolved?
When did Ancient Egyptian religion finaly died out, and who were the last believers?