OK, you have an HTC One M8x for Taiwan.
In order to get the latest Lollipop working and nothing broken, you're going to need later radio firmware than what you have.
The only way that I would trust doing that update for your model would be with an RUU for Taiwan or HTC Asia.
Offhand I couldn't find one.
I also ran across conflicting stories about whether or not you'll be able to install M8 roms.
Let's assume that you can and try to get you up and running, and worry about getting the latest and greatest after that.
Download ViperOneM8 version 3.2.1 (not the latest 4.3.0) from the previous roms link here -
http://venomroms.com/htc-one-m8/
In TWRP, Mount, mount the internal storage or sd card - your pc ought to be able to see it at that point.
Copy the ViperOneM8 zip to the phone.
TWRP, Install - choose the rom.
Choose from within the ViperOneM8 installer -
* International or GSM for carrier.
* Full wipe.
* Stock rom (just as it is, don't try to customize it when given the opportunity).
See if that gets you up and running ok.