All data deleted after upgrading to v8.0 via Jira/Atlassian

After upgrading "Zephyr - Test Management and Automation for Jira" via Jira/Atlassian all of our data has been deleted from Zephyr - tests cases, cycles everything

The app showed as disabled, but after re-enabling nothing was brought back. I tried using links that I had saved elsewhere, but these cannot find the test case etc.

I tried adding a new test case to see if this made anything happen, but again no luck.