Should a Sql Server be accessible through the service's virtual network name?
Given CLUSTER_1, with NODE_1 and NODE_2, and virtual network VNN_1 with IP_1, these will work:


VNN_1\INSTANCE
IP_1\INSTANCE


These will not work:


CLUSTER_1\INSTANCE
NODE_1\INSTANCE
NODE_2\INSTANCE


If you are unable to connect using VNN_1\INSTANCE then, can you ping it, and what does it resolve to? Is it configured for a single IP (i.e. not multi-subnet)?