3405998 - HTTPS connection "Not Reachable": Unsupported or unrecognized SSL message

The HTTPS system mapping in cloud connector is showing "Not Reachable" due to following error in ljs_trace:

2023-11-27 08:57:03,216 +0800#INFO#com.sap.scc.tomcat.utils.SystemPrintStreamSSLWrapper#AccessControl connection checker#          #javax.net.ssl|SEVERE|43|AccessControl connection checker|2023-11-27 08:57:03.216 CST|TransportContext.java:369|Fatal (UNEXPECTED_MESSAGE): javax.net.ssl.SSLException: Unsupported or unrecognized SSL message (
"throwable" : {
  javax.net.ssl.SSLException: Unsupported or unrecognized SSL message
      at sun.security.ssl.SSLSocketInputRecord.handleUnknownRecord(SSLSocketInputRecord.java:448)
      at sun.security.ssl.SSLSocketInputRecord.decode(SSLSocketInputRecord.java:174)
      at sun.security.ssl.SSLTransport.decode(SSLTransport.java:111)
      at sun.security.ssl.SSLSocketImpl.decode(SSLSocketImpl.java:1320)
      at sun.security.ssl.SSLSocketImpl.readHandshakeRecord(SSLSocketImpl.java:1233)
      at sun.security.ssl.SSLSocketImpl.startHandshake(SSLSocketImpl.java:417)
      at sun.security.ssl.SSLSocketImpl.startHandshake(SSLSocketImpl.java:389)
      at com.sap.scc.tcs.e2e.BackendCheckHelper$TLSSecuredBackendCheckHelper.check(BackendCheckHelper.java:133)
      at com.sap.scc.tcs.e2e.HttpBackendChecker.check(HttpBackendChecker.java:58)
      at com.sap.scc.tcs.e2e.SccEndpointValidator.checkConnection(SccEndpointValidator.java:85)
      at com.sap.scc.tcs.e2e.SccEndpointValidator.checkEndpoint(SccEndpointValidator.java:71)
      at com.sap.scc.servlets.AccessControlServlet$3.run(AccessControlServlet.java:564)
      at java.lang.Thread.run(Thread.java:838)}

or

2023-11-27 08:57:03,850 +0800#INFO#com.sap.scc.rt#AccessControl connection checker#          #SccEndpointValidator failed to establish connection to HTTPS://test.sap:8080
iaik.security.ssl.SSLException: Invalid SSL message, peer seems to be talking plain!
    at iaik.security.ssl.ab.e(SourceFile:361)
    at iaik.security.ssl.y.f(SourceFile:365)
    at iaik.security.ssl.n.b(SourceFile:729)
    at iaik.security.ssl.n.a(SourceFile:1503)
    at iaik.security.ssl.y.d(SourceFile:784)
    at iaik.security.ssl.SSLTransport.startHandshake(SourceFile:569)
    at iaik.security.ssl.SSLSocket.startHandshake(SourceFile:386)
    at com.sap.scc.tcs.e2e.BackendCheckHelper$TLSSecuredBackendCheckHelper.check(BackendCheckHelper.java:160)
    at com.sap.scc.tcs.e2e.HttpBackendChecker.check(HttpBackendChecker.java:58)
    at com.sap.scc.tcs.e2e.SccEndpointValidator.checkConnection(SccEndpointValidator.java:85)
    at com.sap.scc.tcs.e2e.SccEndpointValidator.checkEndpoint(SccEndpointValidator.java:71)
    at com.sap.scc.servlets.AccessControlServlet$3.run(AccessControlServlet.java:564)
    at java.lang.Thread.run(Thread.java:838)

SAP Cloud Connector, all versions.

javax.net.ssl.SSLException: Unrecognized SSL message, plaintext connection? , KBA , BC-MID-SCC , SAP Cloud Connector On-Demand/On-Premise Connectivity , Problem