we just had this pop up also.
you have to go under voip providers, nexvortex, source id tab, and check the source identification by DID, and add DID, select all., then click ok.
then, in number routing in nexvortex, you add the number in it's mask field. this makes the call look like number@ip, and allows the call to be accepted by 3cx.
under each did added to the did tab, you have to do DID/DDI number/mask option on inbound rule type