Technical Tip: Debug flow utility on GUI does not display output after a firmware upgrade to v7.4.6, v7.6.1 or v7.6.2

In v7.4.6, v7.6.1, and v7.6.2, the first debug flow capture works as expected, but subsequent captures do not generate any output.

For instance, if the FortiGate is rebooted, the debug flow will display output immediately after the reboot. 

However, if the debug flow is run for the second time, no output will be shown.

This issue has been resolved in v7.4.8 and v7.6.3.

Workaround:
Use CLI debug flow commands.

diagnose debug flow filter addr <IP>
diagnose debug flow show function-name enable
diagnose debug flow show iprope enable
diagnose debug flow trace start 99999999
diagnose debug enable

Reproduce the issue.

diagnose debug disable

Related documents:
Technical Tip : Using GUI debug flow tool... - Fortinet Community
Debugging the packet-flow