Registering Add-ons to Jira Dashboard for Jira Cloud

I am trying to add an add-on to the Jira Dashboard using the sample app that Jira provided on Atlassian Labs and got a 401 when I used the jira service account and password. I get a 404 if I use Jira service account and API key.
Here is the full link:

https://emailaddress:password@{website}/rest/plugins/1.0

Code that I am currently running:
https://bitbucket.org/atlassianlabs/atlassian-connect-jira-dashboard-item-example/src/master/

Actual Error:
Failed to register with host https://{JiraWebsite}/rest/plugins/1.0/ (401)
Add-on not registered; no compatible hosts detected