Help M8 Harmon Kardon edition (Sprint) will not upgrade to Marshmellow

[Arbiter]

Hi folks,

The other half and I upgraded to HTC 10's and she gave my son her HTC One M8 Harmon Kardon edition. It has been getting notifications for months to upgrade to Marshmallow OTA. I download the update, click install, it reboots, start the installation, then stops saying unexpected contents were found in the youtube.apk.

I have tried doing a factory reset and installing.
I have tried downloading the update from HTC and installing from, my PC

Nothing.

Suggestions?? Thanks everyone.

-Jeff