Can't update to Monterey.

When I try to update to Monterey I have an issue after the pc restarts . The blue bar from the update goes all the way and then restarts but then it boots from "MachintoshHd" and after some lines the pc restarts and if I try to boot again from the "MachintoshHD" it does the same thing. I am able to boot to BigSur again with no problem but I just can't update.