In case Default/Custom assigned Keyboard shortcuts are not working:

  • Goto Tools > Workspace > Customize > Options and try to re-load your workspace by clicking Load From button. 
  • If you want to set default workspace Click Default button. Application will reload to default configuration.
  • If this does work you may need to delete the built-in folder, See solution Rebuild Built In Folder .But, you will lose all customizations and have to reset things to your liking.