In case, when we can not reproduce reported issue, we will ask you for application logs. We use this file to investigate what went wrong and if there is any trace of the error.
For a better and faster support, please include it in support request.
From Jira we need: atlassian-jira.log
Where to find it: https://confluence.atlassian.com/adminjiraserver/logging-and-profiling-938847671.html
If you don't have direct access to server, as Jira Administrator, you can use build in support tool to create support .zip file. You can find it in Troubleshooting and support tools:
From Confluence we need: atlassian-confluence.log
Where to find it: https://confluence.atlassian.com/doc/working-with-confluence-logs-108364721.html
In some cases, we will ask you to enable additional logging levels for our application, if attached logs, do not provide sufficient information.