The red light is the Low Battery indicator.
* When replacing batteries, use only new, fresh, premium quality alkaline batteries. Regular cheap flashlight batteries are not suitable.
* Batteries have limited shelf life. Check that the batteries are not past their use-by date.
* Beware of counterfeit batteries. These look just like premium quality batteries from well known brands but have inferior performance. They are often sold at convenience stores, sometimes at suspiciously low prices.
* If you are positively sure the batteries are OK, and the camera still won't work, check the contacts in the battery compartment for corrosion. Clean if necessary.
* If all else fails, have the camera checked. The camera may have developed a problem that causes excessive power consumption, thereby loading the batteries down.