3671008 - Connection was forcibly closed by the remote host when adding a DataSphere subaccount to SAP Cloud Connector(SCC)

Post adding, or while adding a DataSphere subaccout to SAP Cloud Connector, it fails, and following is perceived from SCC trace (ljs_trace.log / scc_core.trc).

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20xx-xx-xx xx:xx:xx,xxx +0000#INFO#com.sap.core.connectivity.tunnel.client.handshake.ClientProtocolHandshaker#tunnel-client-32-8#          #Sending handshake request for tunnelId: account:///<subaccount-ID> and host: connectivitytunnel.ingress.xxx-xxxxx.xx-xxxxx.shoot.live.k8s-hana.ondemand.com:443
20xx-xx-xx xx:xx:xx,xxx +0000#DEBUG#com.sap.core.connectivity.tunnel.client.AbstractClient#tunnel-client-32-8#          #Handshake failed! Closing channel [id: 0xe5296c7b, L:/<local-IP>:<local-port> - R:connectivitytunnel.ingress.xxx-xxxx.xx-xxx.shoot.live.k8s-hana.ondemand.com/51.8.245.21:443] immediately.
java.io.IOException: An existing connection was forcibly closed by the remote host
    at sun.nio.ch.SocketDispatcher.read0(Native Method)
    at sun.nio.ch.SocketDispatcher.read(SocketDispatcher.java:43)
    at sun.nio.ch.IOUtil.readIntoNativeBuffer(IOUtil.java:223)
    at sun.nio.ch.IOUtil.read(IOUtil.java:192)
    at sun.nio.ch.SocketChannelImpl.read(SocketChannelImpl.java:385)
    at io.netty.buffer.PooledByteBuf.setBytes(PooledByteBuf.java:255)
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• SAP Cloud Connector(SCC) release independent;
• SAP Business Technology Platform(BTP);
• SAP DataSphere.

SAP Cloud Connector, SCC, CC, cloud connector, JVM, firewall, proxy, squid, 3128, network, netmask, Region, BTP, IP address, IP, hosts, hanacloud.ondemand.com, k8s-hana.ondemand.com, ClientProtocolHandshaker, com.sap.core.connectivity.tunnel.client.handshake, Unexpected exception, io.netty.handler.ssl.SslHandshakeTimeoutException, handshake, hand shake,  , KBA , BC-MID-SCC , SAP Cloud Connector On-Demand/On-Premise Connectivity , BC-CP-CON , Cloud to On-premise Connectivity service , DS-DI-CON , Connections , Problem