phone stuck in fastboot mode when i updated my recovery from twrp3.0.2.0 to 3.1.0.0.......

[AC Question]

if i attempt to reboot it again goes to fastboot mode and gets switched off.........when connected via datacable to a computer or when it is charged ...it stays in fastboot mode......i have tried all button combos....but none works....if just reboots to fastboot mode with full vibrations and gets turned off.........help needed guys