Authentication Key for my site

[Deleted user]

I' m using the below url https://jira.charter.com/rest/greenhopper/1.0/rapid/charts/scopechangeburndownchart?rapidViewId=4401&view=reporting&chart=burndownChart&sprintId=16899 

to make rest api key in my app. I' m the admin for this project but I get a 404 error. I can use the same url and my credentials I postman to generate json key.

I need help generating a authentication token and download data without errors. Please advise.

thanks

Mythili