Suggestions:
Ensure the account used to add the node has administrative privileges on all nodes of the cluster.
Ensure all nodes can communicate with each other. You can use Ping Command for this.
Ensure that the firewall settings on all nodes allow necessary ports for SQL Server and clustering.
Check Cluster Configuration
Get-ClusterLog -Node <NodeName> -TimeSpan 5 -Destination <Path>
Check Cluster Nodes
Get-ClusterNode
Check Cluster Network
Get-ClusterNetwork