How do I install the OTA update on my HTC ONE M8 AT&T?

[Carlington Spence]

Unable to install OTA update on my HTC ONE M8 AT&T

I woukd like some help on how to update my HTC ONE M8. I root my phone and decided to unroot it following a online video from "the inlockr" after unrooting the phone now shows in fastboot "tampered....relocked" i was able to download the ota update but when i hit the button to install it goes into the fastboot screen and it doesnt allow the update to run instead it stays at the fastboot/hboot screen. I can select recovery and it will run a screen very fast which i am unable to read...but comes back to the hboot screen and also gives me an option to reboot and ill be able to reboot and get back into my phone but it will not update. I installed the stock recovery for my cid and it still doesnt allow the update. I am on software #1.12.502.18... I get no error messages... and i am still S-ON/ it keeps going back to the fastboot /HBOOT Screen and that's it... no update gets install and no error messages.
Can anyone help me please to get my OTA updates to take. Thank you in advance for your help.