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Since the flash is software based to turn it on, some installed apps can prevent the flash from working. Usually this is due to security features, or lack thereof. You can reset your phone back to factory settings, be sure to back up your data. Copy your pictures and music to your computer with a USB cable.
If you use Gmail, your data is already backed up, only if you are signed into your Gmail account on your phone. If you do not have a Gmail account, go to Gmail.com and sign up, then sign in on your phone, and wait to do the reset until tomorrow.
Sign into Gmail on your phone, and your contacts will automatically restore. Let me know if the flash works. If not, it is a hardware failure.