Sometimes the chargers people use are like the cheap jumper cables they sell. too thin to carry the needed current andf the chargers don't put out enough amps to charge the battery. A load test will tell if we have a good battery(parts places can do that for free). If it is good a quick old time test would be a slight rap on the starter to see if the contacts are giving us the no start. Many a GM starter has worked after that trick, although they usually still need to be replaced.
right under the front of the engine.