VirtualBox: kernel driver not installed (rc=-1908)

 This is deja vu - I'm sure of it.

 By now I've seen the pattern behind this error, which prevents a VM (mine's an Ubuntu 20.04) from starting.  It always happens after a macOS (host) upgrade, which would usually have a new kernel version I think, thus requiring the kernel extension for VirtualBox to be upgraded - at least that's my theory.  So I downloaded and installed the up-to-date version of VirtualBox.  The first time launching of the app after installation prompts an upgrade of the extension pack, which is handy!  I finished that, and hit the Start button.  Same error.  😢😢

What I forgot (not the first time) is this:

The OS automatically blocks the new extension until it's authorized here in the Security app.  I vaguely remember the VBox upgrade installation would remind me, but not this time at least.  Hopefully this has a better chance being committed to my memory after I write it down on a post.

Last thing to remember - restart the computer after the extension is allowed so it can take effect.  Then I'll have the sweet moment of finally getting back into my VM!
 

VBox audio driver for Windows 7 x64

I downloaded it from here. It's a Realtek chip. Please note the driver is unsigned (not recognized by Windows 7).