A company is setting up B2B instant messaging capability using a secure client integrated into...

A company is setting up B2B instant messaging capability using a secure client integrated into the on-premises Cisco communication platform. During the setup, the engineer discovers that external Usages from other businesses do not seem to reach the Cisco Expressway for instant messaging, but B2B calling seems to be working Internal chat between clients and chat toward clients is king m home offices using Mobile and Remote Access The engineer verified that the correct ports have been configured on the Cisco ASA, and the firewall rules on the expressway show no cation of any traffic What is the cause of the issue?