Are you using a self-hosted Taiga instance, or tree.taiga.io ?
If you are using a self-hosted version, please make sure you have enabled the Jira section of the importers in both taiga-front and taiga-back. Also, make sure that the URL you set in Jira is your own.
Maybe this other thread can help you Is there any more in depth guide on how to configure Jira project import?
Regards!
