Attempt to join queue failed

"You will not be allowed to join the queue because you are currently assigned to an existing game."

I decide to queue up with a friend and play some normals, but this error message came up. In fact, its come up twice over the past few days. Now I have to wait 5 minutes because of the dodge penalty. This is actually the first time I have encountered this issue in patch 4.21. Any help would be appreciated. Thanks