Flashed HTC One M8 Stock Recovery, Updates Result In Red Exclamation Mark

Hello! This is my first post here, mostly driven by my need to download a patch for Stagefright.

My bootloader is unlocked and I am rooted. I was running TWRP up until now, but I want to patch stagefright so I decided to re-flash the stock recovery. Now, whenever I allow my phone to update, it goes straight to a red exclamation mark inside a triangle.

Firstly, I have an AT&T HTC One M8. Here is what fastboot says:

S-ON
HBOOT: 3.19.0.0000
Radio: 4.0.U60511@50319A
OpenDSP: v47.2.-00564-M8974_F0.1024

My OS and other software versions are

Android 5.0.2

HTC Sense: 6.0

Software: 4.28.502.1

HTC SDK API level: 6.55

Kernel Version: 3.4.0

Baseband Version: 4.0.U605611

Build Number: 4.28.502.1 CL51189 release-keys

I would greatly appreciate your assistance. As it stands, I am very stressed out.