First off, you'll want to make sure you have the most up to date oQueue.
Easiest way to update might be Icebox: https://solidice.com/icebox .
Once update, when you log into the game you will want to look for any errors in your chat. If there are any oQueue errors, its not going to work. Also, you will want to check that the version at the top center of the addon, does not say "X.X.X". If it says X.X.X there was an error, normally related to your realm list which caused oQueue to not load properly.
Check your connection by click the find premade tab. On the bottom right you will see two numbers. One indicating # of people on your friends list who use oQueue, and one indicated the # of people on your realm using oQueue. Each number should be above 10 for the best connection to the mesh network.
To increase the # of people you are connected on your friends list, you will want to press the find mesh button. The find mesh button will try to add 3 - 5 people to your friends list whom have been online and use oQueue in the last hour. This relies on Battle.net to work, so if there are any Battle.net complications, it may fail.
To increase your # of realm connected oQueue users, on the setup tab, make sure you have "Auto join oQueue channel" checked, in the list of check boxes. This will make you join the realm wide oQueue chat that transmits messages behind the scene's across your realm. Along with this, you will want to make sure you are actually joining the channel by right clicking your chat tab and seeing if it is in the list of joined channels. You do not need to view the messages in this channel, but you do need to join it.
Let me know if any of this helps.