The third queue (QueueC) doesn't have any consumer attached from ProxyC and I don't know whyTry renaming ProxyC to say ProxyC1 and activate the session. This will create a new underlying MDB for the jms proxy and you will see consumers getting set on the queue.. Faced this issue many times in our production environment and easiest workaround we found was to rename the proxy service [ toggling enable/disable proxy doesn't seem to have ny effect).. you can change the name to the original proxy once the consumers are set..
We also experienced a problem similar to this. This occurs when you use same work manager with a max thread constraint in the dispatch policies of 2 more proxies.. This imposes the max thread constraint across all the proxy services.I experienced a similar problem earlier where proxy was not getting enough threads to start/initialize itself and hence polling was not working.