Why isn't my HTC M8 working (it goes to reboot screen) after upgrading to Android 6?

[AC Question]

HTC M8 not working (it goes to reboot screen) after upgrading to Android 6

Hi, I bought this unlocked phone one month ago in Canada.

Last week I was in Switzerland and I tried to upgrade to Android 6.
After the upgrade, the Android Recovery screen appears every time I turn on the phone.

I did a factory reset, not working.

When going to the BootLoader screen, this is how the screen looks like:

*** SOFTWARE STATUS: OFFICIAL ***
*** LOCKED ***
M8_UL_CA PVT SHIP S-OFF
CID-11111111
HBOOT-3.19.0.0000
.
.
.
OS-6.12.401.4

As you can notice, I'm not an expert but I'd like to know what should I do to make it working again.

Thanks very much for your help. Much appreciated.
Gerardo

PS: if you need more data, just let me know.

 

[B. Diddy]

Re: HTC M8 not working (it goes to reboot screen) after upgrading to Android 6

Welcome to Android Central! Was it an official over-the-air system update, or did you download it from somewhere and try to install it manually?