Dell SupportAssist

Follow this Guide from start to end do not miss any steps 

You may find that a few thing I am recommending to delete are already deleted from your computer so skip those steps.  

1 Use Microsoft's Installer : 

This step is crucial as Microsoft's uninstaller disables the services as well. Choose SupportAssist and uninstall, Uninstall Dell updates by running the the uninstaller again. If Support Assist doesn't show in List ignore this step. 

Reboot (important) 

1. Delete following folders and ignore the once which are already deleted. 

C:/ Program Data/ PCDR 

C:/ Program Data/Supportassist 

C:/ Program Data/Dell/Dell data volt 

C:/ Program Files/ Dell/Supportassist 

C:/ Program Files/ Dell/ Dell data Volt 

C:/ windows/Temp (everything inside the folder 

Remove these Registries 

Navigate to HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services key.

Delete Dell hardware service, Delete Dell client management service, Delete Dell updates. 

Reboot 

install SupportAssist 

Since the release of the new  version of SupportAssist it have had problems with the installer. My advice is to wait for dell to fix the installer. When fixed it should install automatically as before. I have stopped trying to find a solution for this SA update. 

Followed your directions to the 'T'.  Still ended up with the SupportAssist installer(after a very long running process) saying "unable to install.  Any other way to get this to work????

I had this exact issue, and was also unable to manually install a BIOS update or the Dell Update application.  I had to enable the hidden Windows administrator account and everything worked perfectly there, so I suspect either in my case the user account is corrupted, or Dell's done something to bork up the permissions.

To enable the administrator account:

1. Open cmd as administrator
2. Type net user administrator /active:yes and hit enter
3. Log out of your regular user and into the administrator account.  You may have to go through the initial OOBE/setup stuff.  Once logged in, try downloading a fresh copy of SupportAssist, and hopefully it should work!

Edit to add:  After installing SupportAssist and the Dell Update application in the administrator account, switching to the regular user and trying to run Dell Update there resulted in an error saying that the Dell Client Management Service was not running.  I opened services.msc and enabled it, and set it to start automatically, and now Dell Update works in the regular user as well.  (I should mention that by 'regular user' I just mean the non-built-in admin account - it's not a user without admin privileges).

Can you enable Hidden admin and try above troubleshooting in there. 

In order to enable hidden admin open CMD as admin and type comman 

net user administrator /active:yes

Log out of your account and login to adminstrator. 

Apart from the steps, I have mentioned above. Add one more step. 

Run dot net installer below. 

https://dotnet.microsoft.com/en-us/download/dotnet/thank-you/runtime-5.0.17-windows-x64-installer

Once you run the installer choose to uninstall, reboot and choose to install. Now run supportassist installer.