how to get default settings

Exactly what is no longer working?

@jimmy_5724 as well as per @Michelle Chocolita using the workspaces....you could also reset your Illustrator Preferences, Command K for the Mac, Control K for the PC. This will reset all of your settings to their default values. If you created any  custom settings you've made, such as keyboard shortcuts, workspace layouts, and color profiles, it will be deleted and lost. 

Hi! If you want to reset your workspace go to the upper right of your screen and click Workspace, then choose any of the options you want. More about this topic can be found here: https://helpx.adobe.com/illustrator/using/workspace-basics.html 

Hope this helps!