macOS Big Sur cannot be downloaded
I have the update downloaded, but it says macOS Big Sur cannot be downloaded on "Macintosh HD" I have almost deleted everything off of my Mac to make room for this update. What can I do? The system itself is taking up 77.12GB and Applications is taking up 13GB with 12 of those being the update. I have 25.98GB left open. My mac is currently on macOS Mojave and manufactured in 2017. Any help would really be appreciated.
[Re-Titled by Moderator]