Why is there a red triangle with an exclamation point on my screen? Htc one phone

[Debra Smith2]

Phone will not reboot, just keeps trying to power up and htc one home screen appears for a few seconds then goes black with red triangle.

 

[B. Diddy]

Welcome to Android Central! Which HTC One? M7? M8? Did you get any recent system updates? Is the phone rooted or unrooted?

See if you can boot into Recovery Mode: http://forums.androidcentral.com/ht...ow-reboot-into-stock-recovery-htc-one-m8.html