Hi William,
It does take a while. I'm not sure which command did you use, but it should be with spaces:
DISM.exe*<space>/Online<space>/Cleanup-image<space>*/Restorehealth
You should see a progress and a confirmation after its done. Refer to the photos below:


Also, make sure that you see the system32 in there. It indicates that you were running the command as administrator.
Let us know how it goes.
Microsoft Windows [Version 10.0.17134.829]
(c) 2018 Microsoft Corporation. All rights reserved.
C:\WINDOWS\system32>DISM.exe /Online /Cleanup-image /Restorehealth
Deployment Image Servicing and Management tool
Version: 10.0.17134.1
Image Version: 10.0.17134.829
[===========================85.4%================= ]
Error: 0x800f081f
The source files could not be found.
Use the "Source" option to specify the location of the files that are required to restore the feature. For more information on specifying a source location, see http://go.microsoft.com/fwlink/?LinkId=243077.
The DISM log file can be found at C:\WINDOWS\Logs\DISM\dism.log
C:\WINDOWS\system32>