I am not sure what you are trying to do. Let's see if I understand it correctly.
You have two Nimble arrays and you want to mount one volume of the downstream array to your ESX hosts.
Did you promote the replicated volume or do you want to access a snapshot from the downstream array?
Did the ESX host which is showing the volume have access to the original volume?
Some screenshots could help.
Sorry, but I am not at my desk anymore. Best if you call Nimble support to do a webex.
Normally when this happens ESX is seeing this volume as a snapshot.
Check the following command on the ESX Servers cli:
If the volume shows up it should mount with:
>>esxcfg-volume -M "Volume-Name"