Hi @Dee Akil ,
- First use the Get-SPDeletedSite PowerShell command on your server to find the list of deleted sites and make sure they are indeed in the deleted list.
When a site collection (that is, a SPSite object) is accidentally deleted in SharePoint Server, the deleted site collection is stored in the SPDeletedSite object, not the SPSite object. To restore a deleted site collection, you must use the Restore-SPDeletedSite cmdlet. Make sure you are using the correct command.
Reference: Restore-SPDeletedSite - Reset IIS on all servers in the farm.
- Check the ULS log/event log for more information.
- Try running the configuration wizard to fix.
- Try to detach and attach Content DataBases which having that site collection. Execute it a few times and test(detach and reconnect).
- If you go to the Central Administration to see the site collection details are blank, check that the database uses a standard naming convention and check the permissions on the site collection database for missing values.
- If it doesn't work, the last step is to perform a backup and restore. Recreate the site collection in the CA and overwrite it with the backup. If the web application is broken, you need to restore the backup to the new web application.
Similar Discussion References: Site Collection is missing
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