HTTP Error 500.19 and error code : 0x80070021 at IIS 10.

FIX

Go to C:\Windows\System32\inetsrv\config\applicationHost.config and open in notepad.
Search for a text "handlers".
You will find something like below.
<section name="handlers" overrideModeDefault="Deny" /> change this value from "Deny" to "Allow"


Or 

Search for a text "modules".
You will find something like below.
<section name="modules" allowDefinition="MachineToApplication" overrideModeDefault="Deny" /> change this value from "Deny" to "Allow"

Or Both.