2767055 - Error "Service Not Available" when downloading metadata by using the web dispatcher host

Error "503 Service Not Available" appears when downloading metadata by using the web dispatcher/proxy host.

e.g.  http(s)://<web dispatcher/proxy host>:web dispatcher/proxy port>/sap/saml2/sp/metadata?sap-client=<SAP client>.
The used service to download the metadata is /sap/saml2/sp/metadata.

But the error "503 Service Not Available" is NOT occurring for the following scenarios:

• Access the SAML 2.0 configuration UI via URL using the web dispatcher/proxy host .
  e.g. http(s)://<web dispatcher/proxy host>:<web dispatcher/proxy port>/sap/bc/webdynpro/sap/saml2?sap-client=<SAP client>
  
  
• Downloading the metadata directly via the URL using the application server host.
  e.g. http(s)://<application server host>:<application server port>/sap/saml2/sp/metadata?sap-client=<SAP client>.

Read more...

• SAP enhancement package 2 for SAP NetWeaver 7.0
• SAP NetWeaver 7.3
• SAP enhancement package 1 for SAP NetWeaver 7.3
• SAP NetWeaver 7.4
• SAP NetWeaver 7.5 and higher

SAP NetWeaver 2004 ; SAP NetWeaver 7.0 ; SAP NetWeaver 7.1 ; SAP NetWeaver 7.2 ; SAP NetWeaver 7.3 ; SAP NetWeaver 7.4 ; SAP NetWeaver 7.5 ; SAP enhancement package 1 for SAP NetWeaver 7.0 ; SAP enhancement package 1 for SAP NetWeaver 7.3 ; SAP enhancement package 2 for SAP NetWeaver 7.0 ; SAP enhancement package 3 for SAP NetWeaver 7.0

503 Service Not Available , reverse proxy, sec_diag_tool , SP, IdP , intranet, Web Dispatcher, SAML2 service not accessible, was terminated during SAML2 processing, wdisp/system , /sap/saml2/sp/metadata dowload metadata , KBA , BC-CST-WDP , Web Dispatcher , BC-SEC-LGN-SML , SAML 2.0 for ABAP , Problem