Scoate cardul din telefon mai inainte.
"Press and hold the POWER and VOLUME UP buttons for at least 10 seconds. HTC One M8s then restarts. "
Sursa: http://www.htc.com/uk/support/htc-one-m8s/howto/626424.html
Daca nu merge cu resetare de soft, atunci folosesti hard reset:
1. From the Home screen, tap > Settings > Backup & reset.
2. Tap Reset phone.