
You could try below PowerShell to restore a site collection.
Restore-SPSite <New Site collection URL> -Path <Path of backup file>
If you still get the same error, please follow below tips to troubleshoot the issue.
1.Please check whether the farm account is the part of WSS_ADMIN_WPG, IIS_IUSRS & WSS_WPG groups.
2.Make sure that you are using the farm account and running the SharePoint Management Shell as administrator.
3.Make sure that the farm account has dbowner permission in SQL.
4.If you want to restore the site collection to the same web application from which it was backed up, you need to either delete the original site collection or create a new content database into which the backup can be stored.
References:
https://www.sharepointdiary.com/2017/05/backup-restore-site-collections-in-sharepoint-using-powershell.html
https://sharepoint.stackexchange.com/questions/253468/restore-spsite-the-web-application-at-http-site-could-not-be-found
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