pubnub subscribe error on listen method

[Laluhelmi]

hi @GleasonK ,i had error Can you help me, please!?
at com.pubnub.api.PubnubCore.subscribe(Unknown Source)
at com.pubnub.api.Pubnub.subscribe(Unknown Source)
at com.pubnub.api.PubnubCore.subscribe(Unknown Source)
at com.pubnub.api.Pubnub.subscribe(Unknown Source)
at com.example.l.videocall.PnRt.PnPeerConnectionClient.subscribe(PnPeerConnectionClient.java:106)
at com.example.l.videocall.PnRt.PnPeerConnectionClient.listenOn(PnPeerConnectionClient.java:72)
at com.example.l.videocall.PnRt.PnRTCClient.listenOn(PnRTCClient.java:123)
at com.example.l.videocall.VideoChatActivity.onCreate(VideoChatActivity.java:103)