Cannot send op: 248 Not connected. PeerState: Disconnected in Offline mode

Hi,
I am trying to add groups to the instantiation with:
int[] groups = new int[]
{
1,2,3,4,5
};
PhotonNetwork.SetReceivingEnabled(groups, null);

I call this after I call offline mode = true and join a room. I then get an error on that SetReceivingEnabled line:
Cannot send op: 248 Not connected. PeerState: Disconnected
LoadBalancingPeer:OpChangeGroups(Byte[], Byte[]) (at Assets/Photon Unity Networking/Plugins/PhotonNetwork/LoadbalancingPeer.cs:660)

I'm using Unity 5.4.2f2 and the latest version of PUN+ from the asset store (downloaded this week).
-JJ