This would indicate a problem with Rabbit MQ or your communication to the Rabbit MQ server.
If you have recently had a server move, check that both copies of the messaging.config file has been updated to the new location. These files are usually found in C:\ConQuest Q Series\ and C:\Program Files\ConQuest\On-Screen TakeOff;
The part you're looking for is in the 6th line between an 'at' symbol (@) and a colon. Ensure that there are no spaces before or after the server name.
Diagnosing the issue depends on a number of factors. Please raise a new case online and reference the title of this article.
As this is usually a server-side issue, ConQuest support will probably require assistance from your IT.