Backbone is using a mix of Basic Authentication and Session-based Authentication for Server to Server and Server to Cloud synchronizations. This is working fine for most of the cases. However, more and more companies are changing their security guidelines to require more strict authenticattion mechanisms.
Backbone does not support multi-factor (2FA) or a token-based authentication. This could be, in addition to sending the regular Basic Authentication, we must also provide a token for each request as a second way of verification. Or use a different authentication mechanism like OAuth. This highly depends on the way the 2FA mechanism is setup.
No suggestion available yet. We're waiting for some information & research what kind of token mechanisms are typically used for Jira systems. If you have any hints, please add a comment to this issue, thanks!