Logon screen not showing on fiori launchpad

Hello,

SAP Fiori is accessible on our SAP Server in web browser via URL https://server:port/sap/bc/ui5_ui5/ui2/ushell/shells/abap/FioriLaunchpad.html, a logon screen would appear as shown below by screenshot 1. The logon screen has disappeared when accessing the URL it defaults as user SAP_UI and tile catalog is not showing.

Screenshot 1

Screenshot 2