Well radio, hboot and recovery can only be flashed using fastboot. Thus will never work in recovery, as recovery can just install the corresponding OS.
Regarding the radio you wanted to try. Could be the OS is not designed to work with the Taiwan radio bands, or AT&T doesn't work with them in the region you're in at the moment. Another guess is, that the whole rest of your firmware, as well as you current stock ROM don't support the radio and you thus won't be abled to use it.
Sent from my HTC One_M8 using XDA Free mobile app
Mobile: One M8 Gunmetal: UNLOCK - S-OFF (SunShine) - WWE
CID: HTC__001 (T-MOB101)
FW: 2.22.401.5 (22.214.171.124)
ROM: Stock - SuperSU
Retired: Desire (CWM, Cyanogen), Sensation (Unlocked, S-On, CWM, root), One X (Unlocked, TWRP, Cyanogen), One (M7) (firewater S-Off, TWRP, ViperOne), Moto G (Unlocked, S-On, CWM, CM11), One (M8) GER Silver (SunShine S-Off, TWRP, ViperOne 2.2.0).