3101052 - SAPUI5 App hanging/blank Error: net:ERR_FAILED or NavigationHandler: UShell service API for CrossApplicationNavigation is not available or CORS

• Non-Standard SAPUI5 application hanging or getting blank screen
• An upgrade of an older SAPUI5 (non-standard application) Front End System 4.0 to FES 6.0 sometimes causes the application to hang
• It works for some users and fails for some users
• Example:
  • Users in the field may have devices that are internal (company related)
  • Other users in the field may be external users (like a vendor) who may need to access the application using non VPN
  • What happens is on some users (internal who uses VPN), the application works without issue
  • For external users who do not need to use VPN, the application (SAPUI5) may hang on certain navigation (like tabbing to other parts of the application) and it does not get the values from the services
• Typical error that is seen (it could be different types but these are the general Chrome dev tool traces):
  • There is always a Network Error - net:ERR_FAILED
  • Then followed with NavigationHandler: UShell service API for CrossApplicationNavigation is not available
    
    
    ~~~~~This is the hang point~~~~~~~~
    
    
  • At this point the SAPUI5 application is hanging and it just does not work
  • Please note that if the user is using VPN access to the application, it works and only people not using VPN is failing
  • When working another error or warning shows up tied to CORS security but eventually it will work
    
    ~~~~Chrome Network trace when working with VPN~~~~
    

    Now if we compare it to a working VPN connection, it will show something like this.

    ..
    ..
    style.css
    CORS issue....<-- It always show the CORS
    ..
    ..
    Continue on loading
    and it will work.
    
    Note: Compare this trace with the non-working picture above or hang point.
    ~~~~~~~~~~End~~~~~~~~~~~~~~~~~~~~~~~~

• SAPUI5 1.71.13 or later
• S/4HANA ONPREMISE 1709 SP2
• SAP Front End Server (FES) 6.0 

  "SAPUI5 net:ERR_FAILED","FES 6.0 blank","SAPUI5 hanging","SAPUI5 VPN","SAPUI5 NON-VPN","UShell service API for CrossApplicationNavigation is not available","how to force a network load","sap-ui-debug" , KBA , CA-FLP-FE-AI , Application iframe communication in FLP and Work Zone , CA-FLP-ABA , SAP Fiori Launchpad ABAP Services , Problem