VirtualBox Guest Additions do not appear to be available

[timg]

I have a Ubuntu 16.04 LTS Guest under a Windows 10 host. I just updated the Guest (it updated the kernel to 4.4.0-116-generic).
My Virtual Box manager on the host is 5.2.8 (just updated)

After the updates to the Guest, VirtualBox Guest Additions are not working.

I downloaded VBoxGuestAdditions_5.2.8.iso, mounted it in the guest and ran the installer, (completes normally - no errors), and rebooted the guest.
VBGA still does not work. I have the banner at the top of the desktop that says "VirtualBox Guest Additions do not appear to be available..."

I saw another suggestion to try "sudo VBoxClient-all stop" followed by "sudo VBoxClient-all start"
That results in "sudo: VBoxClient-all: command not found"

What else can be done to restore VBGA?

Edit:

The VirtualBox user manual says:
"If you suspect that something has gone wrong, check that your guest is set up correctly and try executing the command
rcvboxadd setup "

The result looks very similar to the installer, except it outputs:
modprobe vboxguest failed

Here is the log output (sorry for image, but no clipboard or shared folders)



https://i.imgur.com/fSxbver.png

[mpack]

There is no need to download the GAs, they came bundled in the original download. Just follow the instructions in the user manual to install them.