I flashed a CM11 nightly on 3/6/14 and it all but wrecked my LTE/4G connection. Worked great up until that flash.
I've done everything, as far as even bringing it back to my local USC store where they tried a new SIM and restoring back to their software image, *228, everything we could think of.
Nothing wants to bring the connection back.
There are more details here at the CM forum on this (Here)
I fear I may have to get a new phone to actually rectify this situation.
Anyone have any ideas?