hi Marvin.
i had exactly same situation that you, how i resolved? uninstall Norton 360 first,(in your case Norton AV) then turn off firewall.
after this you must erase all temporal files in Windows Setting-Systems-Storage-Temporal Files, select all and erase.
after all this you don´t need to reset computer, just try again, automatically you will receive this notification.
2021-07 Cumulative Update Preview for .NET Framework 3.5 and 4.8 for Windows 10 Version 21H1 for x64 (KB5004331)
you must install this first. (if systems starts by itself installing the windows version 21H1 you must wait for the error and try again but in this time starting with .NET Framework.
to avoid any inconvenient I recommend turn of the features of NET Framework in features of windows.
then will continue with the nightmare
2021-07 Cumulative Update for Windows 10 Version 21H1 for x64-based Systems (KB5004237)
even you will have the option to install this one
2021-07 Cumulative Update Preview for Windows 10 Version 21H1 for x64-based Systems (KB5004296)
I suggest do it.
good luck. :)