Why isn't my Nokia Lumia 525 updating to WP 8.1?

I have a Nokia Lumia 525. It's working on WP 8 at the moment. When i try to update it from the settings , after 2-3 minutes , i get an error message that says "there is no internet connection ".
But the phone is connected to internet.All other applications can reach the internet without a problem.

Any ideas what the problem may be?

Are you using WiFi or cellular data.
If you need to download more than 100 mb you need WiFi. It can not be done with cellular data.