Unable to remove Node from AlwaysOn FCI

Need to remove 2 nodes from a AlwaysOn FCI cluster with the view to uninstall/reinstall different version of SQL Server but unable to remove.

Using normal method of setup files, maintenance, node from cluster, next step successfully passes all checks then when I reach the "remove a node, specify an existing SQL Server failover cluster cluster to modify" It does not dynamically find a SQL Server instance name and therefore unable to proceed.

To fix I have, launch setup.exe as administrator, my account has log on as service permissions, checked all permissions, used another ISO and several other things but still cannot get it to work. Any ideas?