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Do you have mobile data turned on? Over wifi depending on your upload speed it could take a while to upload.
 
Yes, mobile data is on, but wifi is usually faster than the mobile data.
That really depends on your provider having a nice fast connection speed is always slower on the upload speed unless you pay for specific service. For example my connection is 156 down 5 up.
 
From Apple's iCloud Photo Library FAQ http://support.apple.com/HT204264 (with my emphasis added):

When you turn on iCloud Photo Library on your iOS device or Mac, your photos and videos will upload after you connect to the Internet with Wi-Fi and your battery is charged. You can see the status and pause the upload for one day when you follow these steps:

  • On your iOS device, tap Settings > iCloud > Photos.
  • On your Mac, click Photos > Preferences > iCloud.
Depending on your Internet connection speed, the time it takes for your photos and videos to appear on the Photos app on iCloud and all of your devices might vary. Make sure you turn on iCloud Photo Library on each device.
 
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