Solution
If you have used more than one instance during the course of performing the simulator tasks, you may need to repeat some tasks again where you created something like an indicator which is then used later on.
Anything that was done in the previous instance will be 'missing' in the new instance and would need to be performed again, like creating a indicator which is one of the earlier tasks.
This is an example task which is performed early and then the indicator is used later on in the course:
Create New Indicator Manually
To avoid this scenario, try to finish the tasks in the allotted time on the same instance or use the 'extend expiration' link on the course page to extend the instance.