Not able to connect to the server from program-C#

We have a Couchbase server installation in Kubernetes cluster. From .Net we are connecting using

_cluster = await Cluster.ConnectAsync(_options.ConnectionString, _options.UserName, _options.Password);

We are getting an error

System.AggregateException: ‘Cluster has not yet bootstrapped. Call WaitUntilReadyAsync(…) to wait for it to complete.’

But when we connect thru UI (dashboard) it is getting connected.

What may be the issue? Will it be something about the port? Do we need to open any ports?

WaitUntilReady will show the underlying exceptions. Couchbase uses the ports listed at Couchbase Server Ports | Couchbase Docs. It bootstraps from ports 11207/11210