The official HTC ROM updates will only work with SIM free Diamonds, rather than operator supplied ones.
You can install this to operator supplied phones, but you need to update the bootloader (=BIOS) first, by installing a program called HardSPL.
This cna be found
Here on XDA-Developers. We recommend the 1.24 version.
Be warned that sometimes, a HardSPL installation will hard reset your device back to factory settings (but a ROM update will do this anyway!) though this version doesn't for most users.
Once you have HardSPL on the device, then you can install any other ROM.