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Have you tried using Wi-Fi connection instead? If possible, you may want to check your Mobile Data bandwidth using the Microsoft Network Speed Test App - low bandwidths and poor network connectivity are some of the most common impediments to uploading photos to Facebook through the app.
Another possibility is to use the phone browser to upload photos to Facebook instead of using the App.
In my case, I have only experienced issues uploading photos to Facebook when the mobile internet connection is either weak or unstable.