Just upgraded to Windows 1809, and had to do the usual, i.e.:
 
1. Re-authorise AD2
2. Re-apply my old "DOS" style drive letter to folder mappings
 
Fired up CbB, and ASIO had disappeared, so I figured I had to re-install my Focusrite MixControl v.1.8 software / Focusrite USB driver.
 
However, this time it had absolutely no effect. No ASIO.
 
Uninstalled it, rebooted, re-installed it, rebooted, still no joy.
 
So.... I downloaded the latest beta drivers (v.1.10b3) for the 1st gen: http://beta.focusrite.com/releases/scarlett_mixcontrol/
 
Success!!!
 
So if anyone has the same issue, this is what to do.
 
Note that this software is specifically for 1st gen 6i6, 8i6, 18i6, 18i8 and 18i20.... NOT the 2i2 or solo, or any of the 2nd gens.