REST API calls that uses email in basic authentication to the JIRA Cloud endpoint rest/auth/1/session fails with 401 error on instances that have been upgraded to Atlassian account.
1. Make sure the user can login fine to JIRA cloud and can make REST requests to other endpoints.
2. Access rest/auth/1/session via a rest api call using the same basic authentication with email/password
The rest api call should authenticate and the session information will be retrieved.
The rest api call will fail with 401 error.
You can call this resource using your JIRA username and Atlassian account password. Like this:
If you do not know if your instance has been upgraded to Atlassian account or you don't know your Atlassian account password, you can verify this and reset your password from your JIRA Cloud profile page (https://your-domain.atlassian.net/secure/ViewProfile.jspa)
Several customers are having problems with basic authentication for other endpoints. There is currently no confirmed bug on these endpoints, however some potential fixes have been listed on this comment