Akka Cluster Sharding Error

[sukhmaan rathore]

I am getting the following error on implemeting akka cluster Sharding. We are usin 2.5.2 akka version. How can I potentially debug, streams graph or flows...? 

akka.cluster.sharding.ShardRegion        : Trying to register to coordinator at [Some(ActorSelection[Anchor(akka://DevelopActorSystem/), Path(/system/sharding/BusinessUnitShardCoordinator/singleton/coordinator)])], but no acknowledgement. Total [20] buffered messages.

[DEBUG] [04/16/2018 14:55:42.782] [DevelopActorSystem-cassandra-plugin-default-dispatcher-57] [akka.actor.LocalActorRefProvider(akka://DevelopActorSystem)] resolve of path sequence [/system/sharding/BusinessUnitShard#1286037936] failed

[ERROR] [04/16/2018 14:55:42.783] [DevelopActorSystem-akka.actor.default-dispatcher-21] [akka.tcp://DevelopAc...@10.98.49.170:2551/system/sharding/BusinessUnitShardCoordinator/singleton/coordinator] Exception in receiveRecover when replaying event type [akka.cluster.sharding.ShardCoordinator$Internal$ShardHomeDeallocated] with sequence number [1454] for persistenceId [/sharding/BusinessUnitShardCoordinator].

java.lang.IllegalArgumentException: requirement failed: Shard [12] not allocated: State(Map(),Map(),Set(),Set(),true)