Error calling Webservice, when changing IP address in IIS from * to specific

I have a site with a couple of application setup, that was working correclty that is hosted on a client server, but the client wanted to change the IPaddress in the binding from *(All unassigned) to a specific IP address.

Since then when the application A call the webservice that is in Application B (so using the same Ip address) I receive the error :

Exception information: Exception type: WebException Exception message: The underlying connection was closed: An unexpected error occurred on a send.

If I revert back the Ip address from the specific one to the *(All unassigned) one it work as expected.

My question is : Is it valid to have one IP address in this case, or should it be revert back to * ?

Thank you