Thanks for your reply! This is likely just a permissions issue in JIRA (usually it can be related to a field that non-admins wouldn't have access to but is enabled in the integration, or just a project/issue the non-admin doesn't have access to). Are you on TestRail Cloud or TestRail Server? If TestRail Server, can you enable system debug logs, reproduce the issue, and then send us the log file directly via email to email@example.com so we can review this and provide the specific reason for the error:
If TestRail Cloud, can you send us an e-mail to firstname.lastname@example.org with your TestRail address so we can enable debug logs for your and have you reproduce the issue so we can review this?
We look forward to your email!