UCS Kelvin REST Api url not accessible

I have installed the ‘UCS@school Kelvin REST API’ from the App centre. I have started the application and verified it is in running status.

As per the Kelvin REST API documentation (Welcome to UCS@school Kelvin REST API’s documentation! — UCS@school Kelvin REST API 1.8.5 documentation), I should be able to access the application swagger docs and token using below urls:
I am replacing with the fully qualified domain name of UCS, it says " This site can’t be reached"

I am not able to access the Kelvin REST Api installed… any help or guidance on this would be really appreciated!

Thank you!