You have 90 days from the date your passport was issued to report that you have not yet received it in the mail. If you do not report the non-receipt of your passport within 90 days of the issue date, you will be required to reapply and submit the full passport fee.
The best time of year to see the Northern Lights in Iceland is between the months of September and March. To be in with a really strong chance to witness the northern lights a cloudless, clear sky is the main requirement with the outside temperature being cold but dry.
It is not possible to experience the northern lights when it is cloudy and for obvious reasons there are no northern lights visible during summer when Iceland experiences 24 hour daylight as you need darkness to view the lights.