When you changed the permissions, what accounts or groups did you grant access to? Or did you remove all permissions? You had to leave someone or some group with access.
The folder is on a mapped network drive.
I would suggest that you RDP to the server and log in with an admin account. Then reference the local drive path.
Does the Windows explorer see the folder? Have you tried taking ownership from there? Can you see the permissions?
Try this takeown command. It will make Administrators the owner of all files and subfolders. Once you get access back you can go clean up the permissions with explorer.
takeown /d Y /a /r /f "D:\Data\HR-whatever"