It's probably not something that need to be changed in LISA/DevTest. Search Google for the error, and IBM support sites are listed, saying that the queue is already open and it's in exclusive mode, which means that something else is already subscribed to that queue, and the queue is configured to only have one client.
IBM Knowledge Center
So ...
Has something already opened the queue?
Is the queue in exclusive mode?
How are you going to make sure that your responses come from DevTest rather than the server application?
You say that you created the virtual service from rr pairs. Was this because:
1. The server application doesn't exist
in which case, you will need to investigate what else is subscribed to the queue to force this error
or
2. You needed to create a virtual service in a working environment but were unable/unwilling to use proxy queues
Changing the queues is a standard part of deployment processes, to move from one test environment to another.
In DevTest, we introduce the concept of "proxy queues". This is a convenient short-hand way of saying "create new queues, so we can open the queues in DevTest without having a server application also opening them and causing problems like exclusive opens or other applications consuming and deleting messages before we get a chance to take copies"
Rick