Cant update unlocked htc one m7
I recently bought an unlocked AT&T htc one m7. The phone came with 4.3 and I have been trying to update the phone to 4.4 kitkat. The update is available when I check software updates in settings. Once I download it the phone started to install the update, the phone restarted and showed a green circle made with arrows and a green arrow pointing down in the middle of it with the installation bar below it. Once the bar reaches halfway full a red triangle with an exclamation point in the middle of it pops up and I am unable to install the update. I then hold the power button and it restarts my phone. My phone works fine after this failed process but no update is completed.