Cannot add SQL Listener to Always On

Hi all

Hope someone can assist with my issue. I have a two node cluster running SQL Server 2019 CU14 and the nodes are on different subnets. Always On has been added and working fine however I can't add the SQL Listener, keep getting the following error:

"None of the IP addresses configured for the availability group listener can be hosted by the server 'xxxxxxxxxx'.

Either configure a public cluster network on which one of the specified IP addresses can be hosted, or add another listener IP address which can be hosted on a public cluster network for this server."

The Listener VNN has been created and exists in AD. I can ping it from both nodes and have tried creating it from both Primary and Secondary nodes. I've restarted SQL Server Services AND rebooted both VMs but still no joy.

The Wintel guy checked the cluster and assures me all is healthy and the Cluster Object has FULL permissions on the SQL LIstener but still no joy. Of course the IP address associated with the Listener is not being used by another object and there are no firewalls between the nodes and rest of network so it isn't a port issue (using port 1433).

I've checked MSDN and other SQL forums and followed the suggestions but no matter what I do still always get the above error so any further suggestions or advice would be much appreciated!

Thanks in advance.

Ali