Q: Not updating to El Capitan

Well, you've told us next to nothing, much like going to a doctor and saying "I'm sick, please help!"

So with so little information, about all we can do is see if you meet the El Capitan requirements:

Upgrade to OS X El Capitan - Apple Support

If you do meet the requirements, you should tell us exactly what you have done, what you have seen, what symptoms of failure you have seen, the age and configuration of your Mac, etc.