My HTC One M8 phone has just gotten the Android 6 update (like a week or few ago). I successfully downloaded and unzipped the update. However, I was the confronted with this screen (sorry for the poor resolution, I took it with my iPad since I couldn't screenshot):
I tried to do this multiple times (including recently, which is when I took the photo), and the same thing kept happening. I contacted HTC support, and someone told me to download a ROM onto my laptop and update from my laptop. However, to do so, I also needed to download HTC Sync Manager.
HTC Sync Manager had trouble connecting to my phone. It would start a sync process, but then say that there was an error. After an hour of fruitless research, I tried to update anyway. After a bit of updating, it would say that the update failed, and it would just revert back to the old OS. Frustrated, I said that I would try again later, and uninstalled/deleted everything that I had downloaded.
Trying it again now, I'm getting the same thing. What can I do to circumvent this and successfully update? Everything I've tried, I've tried twice.