I’m trying to use the DiamondCard service as a SIP provider. I have an account with them and their soft phone works correctly on the same machine where I have installed the Voicent gateway.

I asked them for some advice, they suggested to remove the stun server parameter. It didn’t solved the problem.

Can you give me more advice on this configuration ?

You must use a STUN server if the gateway computer and the service is separated by a router. In most cases, you need to specify the STUN server. Some service providers, like diamondCard, do not have their own STUN server, you must use a public one like stunserver.org.

For the rest of the account setup, please see the following figure. Here we assume you have 456789 as your SIP account.