If the light is on the airbag will not work. The system is disabled if the light is on and i think it would not be wise to ignore it.
My bet is that you have the very common issue of the seat connectors. All i do when it comes up every couple of months is to unplug the connectors under the seat, spray them with some contact cleaner and re-plug and they work fine for another couple of months! 10 minute job at the most!!!! It is a common issue on subarus.
Here are the connectors: