This error is most likely occurring because the original board has already been connected to a different instance. While you can have several Jira instances connected to your account currently you can connect your Lucidspark board to only one Jira instance at a time. 

To continue your work you can create a brand new board copy and paste the content of the original board and attempt to import your jira card once more. With this newly created board you should be able to successfully establish a connection with your current Jira instance. 

Useful Resources:

Integrate Lucid Cards with Jira

FAQ’s

I was having this issue and it was because I was trying to use the Jira integration on a board that I had initially created as a LucidCHART. I was using the new feature where you can switch to the LucidSPARK functionality but the Jira integration still would not work. I figured it out after some trial and error of creating some test boards.