After my investigation I didn't find in internet the solution to the problem named in the title of this article.
I found from veeam some information like this article: https://www.veeam.com/kb1756
As you are able to find in internet, this problem appears if the service is down but as I said it didn't work in my case because the services were working properly so i had to investigate more.
Finally the problem was related with the network. I had three nics in my server and Veeam worked fine when I re installed the server only with one Nic enabled and all others disabled. Maybe there is another article detailing the problem but while that, I wanted to share with you the solution I deduced after reading all others.