Here is the newest stock firmware for the M8 quad core tv box, It fix the google play store paid app download problem. You can get the firmware here:
password is geekbuying.com
Download the firmware from the above link. decompress the file.
Prepare a SD card, and format the card, copy the file to SD Card – Make sure your device is powered off and power cable removed.
Insert SD card with extracted files in root directory
Connect your M8 tv box with your TV or monitor via HDMI, so you can check on the screen;
Insert a match or a toothpick to reset button – you will feel a click. (the reset button is in the AV hole in the back)
Power on the M8 tv box by inserting power cable, while holding the match in the reset hole.
it will boot to recovery and now connect a USB mouse with your m8 tv box, and choose update from ext, and then choose update from external sd card, and apply the update.
The system will inform you when the update finished, and then reboot the M8 tv box, and finish the update.
Any questions, feel free to contact us.