Steps
- Start your windows PowerShell on your computer.
- Right click and select Run as administrator option.
- Paste the below script on the PowerShell window and click the enter button.
- Check your SharePoint site Feature will activated successfully.
- Add-PsSnapin Microsoft.SharePoint.PowerShell     
- $w = get-spweb http:  
- $r = $w.RootFolder     
- $r.WelcomePage = "Pages/newmasterpage.aspx"     
- $r.Update()     
- $w.Dispose()   
Run the script with the required administrator privilege.To verify that, Check the output window.
 
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