Hi Maher,
Is it possible for you to share the link to the WMS here?
Are you sure that you have the correct URL? Can you contact anyone at that agency to verify that the URL is correct? Or maybe the service is temporarily down (or maybe the service has changed)?
The same error massage for many , maybe the service link changed from LPI or it is not working ??
It sounds like you may need to contact the organization to see if the link is incorrect or if the service is down.
You could use the following URL (it asks for authentication)
The REST URL that I found is as follows
Imagery/LPIMapIS (ImageServer)