To find your SketchUp Pro license serial number, please do the following based on your operating system. Windows

Situation: You have multiple partitions or hard drives set up on your Mac. After booting into a different partition or drive you're missing your extensions and plugins. When installing SketchUp on a Mac with multiple drives or partitions, we always recommend installing on your root volume. However this can cause problems when booting into another partition. To resolve this problem we suggest one of these two options:

You may see this error when interacting with 3D Warehouse or Extension Warehouse from inside SketchUp. To resolve this issue, please follow these steps:

MacOS To work around this issue, press Ctrl+F7. If you're using a Mac laptop, press Ctrl+Fn+F7. Pressing Ctrl+F7 will disable Full Keyboard Access". If the shortcut doesn't work, go to System Preferences > Keyboard > Keyboard Shortcuts' , select 'Text boxes and lists only' under 'Full Keyboard Access'.