When using multiple monitors especially when changing and unplugging these monitors from a Laptop SketchUp and your laptop’s settings can get confused and hide some of the popups and toolbars. 

The first option is in your windows settings go to Display and under Multiple Displays turn off ‘Remember window locations based on monitor connection’ and then back on again. While in this menu also switch the screen display (So screen 1 is now screen 2). Then reopen SketchUp and see if there is an improvement.  If the issue is now resolved you should be able to switch the screens back without any issue, just remember to do this while the monitors are still connected. 

Other options are to Repair the application. Go to ‘Add or remove programs’, find SketchUp, Modify and follow the pop up and select repair. 

You can also reset your workspace inside of SketchUp. Head to Windows > Preferences > Workspace > Reset Workspace.  Also head to View > Toolbar > Reset All and then restart SketchUp