I think you missed to put FusionAuth Tenant ID.

In my case, I create a file called appConfig.json :

e89f0007-0a18-41d8-b184-5e820eafa09e-image.png

The file contains :

FusionAuth URL (where you deploy your FusionAuth app such as https://login.mywebsite.com) FusionAuth Tenant ID FusionAuth App ID FusionAuth Client Key

Afterwards, I create a new instance of FusionAuth like this (in another file):

d60fe095-14be-4a7e-85fb-44b49a68c462-image.png

I pass FusionAuth Tenant ID here as a parameter.

Hence, I can fire a login function like below :
a4eed8ff-1441-4f15-9a93-9123603c36c7-image.png