Trying to launch media creation tool - "Something happened 0x80070002 - 0x20016"

I was seeing the Something happened 0x80070002 - 0x20016" error (as per image below) when running the media creation tool as well. What worked for me was the following fix from Reddit. I was having to run the tool as I hadn't recieved a notification to reserve a copy and it wasn't showing up in Windows Update until the below change in the registry.

1. Click on Start, search for regedit.
2. With regedit open, proceed to the following path. Computer\HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\WindowsUpdate\OSUpgrade
3. Right click on the right side window and go to New -> DWORD (32-bit) value
4. Rename the new value to "AllowOSUpgrade" without the " quotations and make sure it is exactly the same as it is case sensitive.
5. Double click on the newly created value AllowOSUpgrade and change the value to 1 with hexidecimal base.
6. Close regedit and run Windows Update again. Windows 10 should pop up and you can then download it.

Windows 10 Upgrade Problems: Something Happened Error

Automated fix: Run the Windows Update Troubleshooter.

Manual fix: See below.

Automated fix

Even when users get Windows 10 running on their PCs, they are running into issues. Once issue that happens is simply being referred to as the Something Happened error. It’s called that because that’s what shows up on-screen.

Microsoft has a tool to automatically fix this issue and it is called the Windows Update Troubleshooter. If you’re an experienced user you can manually try and fix this with the Command Prompt by following these instructions.

Source 7 Windows 10 Upgrade Problems & How to Fix Them

Manual fix

This issue might also occur due to corruption in Windows Update component files. I suggest you to reset Windows Update component. Kindly follow the below given steps.

1. Press Windows+X, select Command prompt (Admin) to bring up elevated Command prompt.

2. Stop the BITS service, the Windows Update service, and the Cryptographic service. To do this, at a command prompt, type the following commands. Make sure that you press Enter after you type each command.

   • net stop bits

   • net stop wuauserv

   • net stop appidsvc

   • net stop cryptsvc

3. Rename the software distribution folders backup copies. To do this, at a command prompt, type the following commands. Make sure that you press Enter after you type each command.

   • Ren %systemroot%\SoftwareDistribution SoftwareDistribution.bak

   • Ren %systemroot%\system32\catroot2 catroot2.bak

4. Restart the BITS service, the Windows Update service, and the Cryptographic service. To do this, at a command prompt, type the following commands. Make sure that you press Enter after you type each command.

   • net start bits

   • net start wuauserv

   • net start appidsvc

   • net start cryptsvc

5. Restart your PC and check if it works this time when you try to update.

Source Unable to Upgrade to Windows 10 - Something Happened error

Besides any other fixes presented in these answers, the cache folders for the files needed to create the media should also be erased. Corruption of these files is also a cause of failure to create the media.

Erase the two cache folders present at C:\, named:

$WINDOWS.~BT
$Windows.~WS

You might need to modify the View parameters of C: as to be possible to view hidden and system folders and files.

After this, the Media Creation Tool will download the needed files again.