Hey Cary,
I'm seeing the same issue with the next version of Chrome:
macOS : 10.12.6
Keyboard Maestro : 8.2.4
Google Chrome : 69.0.3497.92 (Official Build) (64-bit)
It would appear that Google has completely screwed up window and tab ID numbers in the newest incarnation, and this is causing Keyboard Maestro's capture-front-window action to choke.
There is a workaround available.
Download ⇢ Chrome -- Take ScreenShot of Front Window to Clipboard.kmmacros (6.0 KB)
-Chris