Hi Jens,
It is strange because if the monitor gets values this means they are connected.
Could you please confirm if my understanding of your problem is correct?
1. You open a scenario
2. Change the load generators status to ready.
3. Set the scenario to start for example after 2 hours
4. Click start scenario button and “Scenario Start Delayed” window opens
5. When the test starts, the status of the monitor over firewall in the load generators list is down and you receive the error messages.
What error messages do you receive?
Kind regards,