3334829 - BTP application connection to data source fails with error: 104 - Connection reset by peer

Trying to setup the BAS (Business Application Studio) to connect to a backend and the connection in SAP Cloud Connector shows as available, in destination the check connection is successful.

However in BAS selecting the data source results the error:
All catalog service requests failed for system: XYZ

• The terminal test for the curl command shows return code 200 
  > CONNECT <host>:<port> HTTP/1.1
  > Host: <host>:<port> 
  > User-Agent: curl/7.74.0
  > Proxy-Connection: Keep-Alive
  > 
  < HTTP/1.0 200 OK

• SAP Cloud Connector ljs trace the following entry appears:
  2023-05-13 03:09:33,155 +0000#DEBUG#com.sap.core.connectivity.tunnel.client.AbstractClient#tunnel-client-124-1#          #Successfully connected channel: [id: ...  - R:connectivity.us20.applicationstudio.cloud.sap/...]. Starting handshake with server.
  2023-05-13 03:09:33,156 +0000#INFO#com.sap.core.connectivity.tunnel.client.handshake.ClientProtocolHandshaker#tunnel-client-124-1#          #Sending handshake request for tunnel: account:///<subaccount ID>/... and host connectivity.us20.applicationstudio.cloud.sap:443
  2023-05-13 03:09:33,157 +0000#DEBUG#com.sap.core.connectivity.tunnel.client.AbstractClient#tunnel-client-124-1#          #Handshake failed! Closing the channel [id: ... - R:connectivity.us20.applicationstudio.cloud.sap/...] immediately.
  java.io.IOException: error 104 - Connection reset by peer

• Business Application Studio
• SAP Business Technology Platform

s4hana s/4hana hana s4 R/3 abap ip ips host firewall network template fiori range address conencted connectivity btp sap cp scp webide web ide cf cloud foundry Odata, V2, V4, , Gateway, OData Version(s)