Setting up Always On Availability Groups with Windows Server Failover Cluster
If I understand your situation correctly, SQL Server isn't even in the picture right now and you're stuck at configuring Windows Server Failover Clustering?

If that's the case, then the best place to look for further clues (as this is quite the open ended question that could take a person many hours to investigate and depend upon settings in your specific environment) would be the cluster log. One of the easiest ways to gather the cluster log is to use the powershell command Get-ClusterLog it can take multiple inputs and I'd recommend using at least -UseLocalTime and -Directory to change the log from UTC to local and the directory that you'd like the logs to be output in, respectively.

Since this, currently, has no involvement with SQL Server the question may be closed to migrated (for future reference).