Can't update S5 topic

I had my S5 rooted a few months ago, but then the update came out that was supposed to fix the bluetooth (last July), and my phone automatically downloaded and tried to install it. My phone was still rooted, so the updated failed. However, my root also failed as well. I could no longer access root applications like Titanium Backup, and towel root told me that it was unable to root my phone. Basically, my phone became frozen in time and was unable to update or do root-level things since this update last July. Now that Lollipop is out, I really want to upgrade, but factory resets do not solve my problem and I do not know of any more permanent way to get my phone back to basics so thatr I can receive OTA updates and have them actually work. Any help is greatly appreciated, as I really do want to upgrade my phone.