This is the official page from which you can Download HTC One M9 Stock Firmware ROM (flash file) package on your Computer.
The firmware package comes as a compressed file (zip file) which contains Flash File, Flash Tool, USB Driver and How-to Flash Manual.
HTC One M9 Stock Firmware ROM (flash file)
Package Name: HTC_One_M9_4.27.651.4_RUU_0PJAIMG_Sprint_7.0.zip
Package Size: 1.79 GB
How-to Flash: Open and exe file from firmware folder and follow the screen instructions.
Firmware Link: Click Here to Get the Firmware
How to Flash HTC One M9 Stock ROM
Step 1: Download and upzip the firmware on your computer.
Step 2: After unzipping the Firmware package, you will get the Firmware (ROM), Flash Tool and Driver.
Step 3: Install the provided USB Driver on your computer.
Step 4: Open the Firmware Folder and launch the .exe file.
Step 5: Connect your HTC One M9 device to the computer.
Step 6: Click on the Next button to begin the Flashing process.
Step 7: Once flashing is done, disconnect the device from the computer and restart it.
[*] HTC Driver: If you want to download the latest version of HTC USB Driver, then head over to the HTC USB Driver Download Page.
[*] Take a Backup: Flashing the above Firmware will delete the personal data from the device and you wont be able to recover it in anyway. Therefore, we recommend you to take a backup of the personal data before flashing the above firmware.