"Not authorized to use " message when project is deployed in local network domain

I have successfully tested the PDF Embed API in my .NET MVC project locally in the visual studio debugger.
The project was deployed in a server with a local IP (local network) but as I could not create credentials for an IP, I asked from our network admin to map this local ip to the domain name dirapserver.xxx.gr.

I then created an new project with the following credentials for PDF embed API 

I am still gettting the same error

and my console output is

The code is correct and futhermore I can see the pdf file for an instance before I receive the error.
So, my basic question is whether I can use the API in a not public network ,with a local domain name?

Thank you in advance