My Windows 10 Version 20H2 will not install the update 0x80004005.

I agree! I am also at my wits end with this. Microsoft needs to come up with a fix. I am beginning to think Apple for my next computer.

:(

Seriously--WAY beyond my expertise level. Microsoft needs to come up with a solution that works for the average user. These updates are supposed to be essentially transparent to the user--not require an advanced degree in system maintenance. Near as I can tell from this thread, this problem has been going on for MONTHS, and I thought I saw the "me, too" count around 2500.

I have a good internet connection, But, I can't download it. Sad to say,I waited 5 hours..😒 But, It still showing this..!

Well this one REALLY annoyed me!  I've been an MCP for a couple of decades, back even as far as Windows NT/98.... yep.  Old and cagey and this stumped me until I read hints about the boot configuration data being hosed.

First, let me say this was a brand new PC, new build, new drives, and NEW Media Creation tool USB bootable drive.  It seemed ok at first until I got notifications about EOL of my version of Win10 that didn't make sense, and I couldn't get the Windows Update or Windows Update Assistant to do anything, it said I was entirely "up to date" on version 1909 that my machine had finally "upgraded" itself to via Windows Update.

My fix:   I booted into command prompt/admin as many of you should know how to do. 

Boot to Advanced Startup Options in Windows 10 | Tutorials (tenforums.com)

And I successfully backed up, exported, my old BCD.  

But instead of commands to rebuild or create a BCD anew, I did the super-secret-special-sauce version of 'sfc'.  Really, there is a special mode -- when I ran sfc /scannow it didn't fix things, but when I added two parameters, it worked like a charm:  How to Fix winload.efi missing or corrupt error in Windows 10 | Tutorials (tenforums.com) <-- I just did the part that's buried, "Run SFC and CHKDSK", just sfc.

The tricks are: 

a) find out what the command line thinks your Windows boot drive is.  If you're having problems, it may well be like mine, things were tidy.  Running bcdedit command will show you the drive

b) using "sfc /scannow /OFFBOOTDIR={yourdrive}:\ /OFFWINDIR={yourwindowsdriveandpath}

After rebooting, I ran the manual Windows Update Assistant tool and this time it worked as designed:

Download Windows 10 (microsoft.com)

I'd never had much luck with sfc before but I sure did this time.

YMMV -- GOOD LUCK!

Used this link and it looks like it's finally downloaded and installed - took several hours but so far looks good! https://www.microsoft.com/en-us/software-download/windows10