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Navigate to SharePoint
Click on any one of your SharePoint Sites
Click on Site Contents Tab on the left side
In the URL Box, copy all the text in yellow below once in Site Contents:
Go to the SharePoint site where you get the 404 error and paste it to the end of the link after the site name
The page will display in the Site Contents screen. Click on Recycle Bin
Next to Home.aspx, tick the radio button
Click Restore
The site is restored