We are using Objective-C.

Thank you Eskimo. However, we are still puzzled as to why this occurs on only one of three iPh X devices that we have available to us. Two of these are also the same Model - MQA82X/A, yet only one of them exhibits this issue. Are you able to shed any light as to why you believe this could be the case? Both have Privacy > Local Network enabled for the application, and both are running the same version of iOS and our application.

Some points which I have not yet raised : The Local Network consists entirely of our hardware; The Network consists of one Access Point, and several End Points; With two of the iPhs we can connect through the AP, to the End Points, successfully; With the 'problem device' we are able to establish a connection with the AP, [so in effect we are successful in establishing a connection, albeit only to the AP], but we fail to connect to devices on the other side of it. The system has been functioning successfully prior to the recent updates.

A further point of clarification: The reason we know we are able to connect successfully to the AP device with the iPh that has the 'issue' is because it is also configurable as an End Point, and we are able to instruct it - eg change LED colour.