Accessing a network share via a SQL Server 2012 Availability Group
CLS is not an alias for either CLS1 or CLS2. CLS is a cluster, not a real machine. You cannot access \\CLS\c$ simply because no such thing exists. There is only \\CLS1\C$ and \\CLS2\C$ and you can access either of them. You should figure out which one is the one you're interested and access that.