Normally you would use Insert Text by Pasting actions rather that the functionally similar Set Clipboard to Text / Command-V.
You can see the variable values using the Variables preference pane in Keyboard Maestro, but Keyboard Maestro also tells you what it will set the values to at the bottom of the Set Variable action.
It is showing you that the variable currently has no value, and if the action were run right now, it would have no action afterwards either.
The tokens look right (unless there is an invisible character in them or something like that), so that would make me think that for some reason Keyboard Maestro cannot communicate with Safari via AppleScript, which is pretty weird (its quite common with Chrome and seems to happen after Chrome updates itself). So perhaps you updated Safari and the AppleScript system has lost its connection to Safari. Try:
- Quitting and relaunching Keyboard Maestro Engine.
- Quitting and relaunching Safari.
Until you can see the current Safari URL in that first action, you're not going to get anywhere.