Win2016 multi site cluster creation - Could not detect if cluster feature is installed on... remote site nodes

I’m trying to build a test cluster with which to test Storage Replicas using CSV using Windows Server 2016 with desktop experience. I want two nodes, with drives shared between them at site 1 and two nodes at a different location (site 2) with drives shared between them.

I’m failing right at the start when trying to create the cluster. I can add two local nodes but I get the error ‘Could not detect if cluster feature is installed on ‘s3srv22.h1.local’ in the Custer admin MMC.
To try to eliminate network and/or remote management I have:

1. Added all 4 nodes into Server Manager on the server I’m working from. All show as Online in Server Manager so I know I’ve got connectivity and rights to access them.
   I used Server Manager to install Failover Clustering remotely from the server I’m working from.
   To be absolutely sure I’ve got all features/roles, I’ve run:

$Servers = 'S1srv11','S1srv12','S3srv21','S3srv22' 
$Servers | foreach { Install-WindowsFeature -ComputerName $_ -Name Storage-Replica,Failover-Clustering,FS-FileServer -IncludeManagementTools -restart }

Result:
Success Restart Needed Exit Code      Feature Result                              
------- -------------- ---------      --------------                              
True    No             Success        {File and iSCSI Services, File Server}      
True    No             Success        {File and iSCSI Services, File Server}      
True    No             Success        {File and iSCSI Services, File Server}      
True    No             Success        {File and iSCSI Services, File Server}

1. I’ve set the Windows Firewall to Allow all incoming connections on one of the remote nodes. I did this for all firewall profiles.
   
2. The Layer 3 firewall between the two locations currently has an allow Any/Any rule to allow all IP4 traffic including ICMP (it does not support IPv6).
   I’ve specifically enabled Network Discovery and File and Printer Sharing on the remote node which I can’t add to the cluster.

RobinG