I managed to successfully integrate Jira Cloud in my app, but the authentication was expiring / timing out very quickly (multiple times per day).
When I'd click 'See token status' on the resource, it would show 'No' in the 'Exists' column.
The way I fixed it was to add 'offline_access' to the resource scope. This is built into OAuth, which took me longer than it should have to figure out.
I figured I'd note it here in case anybody else is clueless like me.