Unable to break far end dial tone when using remote extension

[freddiespencer]

I have a network of PBX's in Spouth America. They are networked using VoIP trunks with Medpro and Clan boards. In most cases I can use the far end remote extension but at some sites I cannot break dial tone and the far end user cannot break the dial tone of this PBX in London. Where should I begin trouble shooting?

 

[artieman]

Check your Medpro resources. Make sure that they are available. Also check your IP-Codec. If they are mismatched, you will not have audio but the call will connect.