I was unable to check for WP 8.1 GDR1 update due to an error named 80072ee7. I checked for problem in my internet connection. The connection was working well. Then I looked for other reasons.
I had installed a lot of apps in the SD card. I just moved them to phone memory. I still had enough phone memory( around 2.5 gb). As soon as I did this, the notification came,"An update is ready to download". So, if you are facing a similar problem, try to move your apps to SD card or remove your SD card before checking for updates. If anyone is curious, I use a Lumia 520.
I had installed a lot of apps in the SD card. I just moved them to phone memory. I still had enough phone memory( around 2.5 gb). As soon as I did this, the notification came,"An update is ready to download". So, if you are facing a similar problem, try to move your apps to SD card or remove your SD card before checking for updates. If anyone is curious, I use a Lumia 520.