Was the bag overfilled before the light came on?
Had you been using it for a long time before the red light came on?
What country are you in?
How old is this, please?
Ok, the red light comes on if the motor has overheated or has a fault.
If the bag is overfull or the hose is blocked, the motor overheats and it will cut out and bring on the red light. Once cooled down it will start again. I suspect this is not the case for you if it has been left to cool down.
If the motor is faulty the red light will come on and will not reset.
Unfortunately the motors for these machines is extremely expensive.
Given the age of the product, I would have to say that it probably isnt worth repairing. Im sorry its not good news
I hope this answers your question