We've checked and ensured that indeed we do have active dependent issues, but none of them are showing on the report.
Any troubleshooting advice would be helpful.
New dependencies may not appear until the plan is calculated. Could you try re-calculating your plan and see if it causes your dependency to appear?
If you're running Jira in Server, there was a bug causing issues to not appear that's been fixed in 2.11.0: https://jira.atlassian.com/browse/JPOSERVER-2069. So upgrading Portfolio could fix the problem.
If that doesn't help, could you raise a support ticket for us to investigate this further: https://support.atlassian.com/contact/
The Portfolio for Jira team