Sierra has introduced some new security features that do some weird quarantine things with applications. In certain situations, it's possible that it's running SketchUp from a temporary "secure" location instead of where it's actually installed, which means that it can't find LayOut for the "Send to LayOut" feature.
To see if this is the issue that you're seeing, do this:
When you see the issue, launch the "Activity Monitor.app" (in Applications/Utilities). Select the running SketchUp.app, then press the Info button. Under the "Open Files and Ports" tab, there you can see whether SketchUp is launched from a randomized location or from where you actually installed it.