hop of those help? Your application isn't requesting any messages, that's why it is not receiving any. Based on the snippet of network trace from your non-working environment, it is only connecting (opening, inquiring and closing the queue manager - which it does during connection processing and after the MQCONN). The connection that was created is then not used - there are no MQGET or SPI flows, just heartbeats.
This might help you Have a look at SupportPac MO72. It is a client-based version of runmqsc called mqsc. If you are suitably authorized (or if nobody bothered to secure the QMgr) then you can do anything with mqsc that you can with runmqsc.
Is it possible to look at received queue messages with the Tibco queue client?