2900689 - Logon button does not work using SAPGUI for HTML or Web Dynpro ABAP application

• When trying to launch SAPGUI for HTML (Webgui) tile from Fiori Launchpad (FLP) unable to proceed into the transaction from FLP.
  
  
• SAPGUI for HTML (WebGUI) service is activated, testing the service directly, after being prompted to enter the user and password and hit Logon (enter), it also does not go any further. It hangs on the logon screen. 
  
  
• Using e.g. Web Dynpro ABAP application after entering the logon credentials and pressing the 'Logon' button no action is triggered.
  
  
• LTMC not working. e.g. browser page shows an error message: "This site is not secure" "Your PC doesn't trust this website's security certificate."
  
  
• Run ESI or Fiori Launchpad, the logon page gives the error  "Logon is being prepared".
  
  
• While calling NWBC, WebGui, and SOAMANAGER there is no logon page but a blank screen only. 
  
  
• The HTTP trace shows 403 Forbidden or 404 Not Found return codes for systemloginjs ICF node, as shown below (403 in this case):

• WEBGUI / SAP GUI for HTML
• Web Dynpro ABAP
• SAP NetWeaver
• ABAP PLATFORM - Application Server ABAP
• SAP NetWeaver Application Server for SAP S/4HANA

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