PFB (ABAP) - ABAP System not available (PFB (ABAP))
Root cause: 
The ABAP system PFB did not respond to availability checks due to a failure in external program connectivity, as indicated by the error 'NIECONN_REFUSED(-10)' when attempting a direct connect to localhost:8900. The external program was either not started or had crashed, despite HTTP connectivity being confirmed as functional.  
 
Resolution steps: 
- Confirmed HTTP connectivity from the system was good, ruling out network issues for HTTP availability. 
- Identified the root cause as a failure in external program connectivity via the error 'NIECONN_REFUSED(-10)', indicating the program was not started or had crashed. 
- Validated that HTTP availability checks passed, focusing troubleshooting on the external program state.