Unable to bootstrap another DC in my cluster

[K F]

Hi folks,
As I am trying to bring up a new DC in my cluster, my first seed node that I 
bring-up in the new DC that I am adding to the existing cluster. It's not able 
to receive reply back for the GossipDigestSyn request sent to other seeds in 
the cluster.
This is causing the first node to come-up as a standalone node in the cluster. 
So, how do I debug further this situation?
I am running 2.0.14 version of cassandra. Is this a known issue with this 
release?
Thanks.