This is a working mod to fix disappeared 4G LTE connection in Redmi 3 (IDO) running MIUI 8 ROM. This 4G mod is known to work flawlessly in reactivating 4G network of IDO device running MIUI 8 v6.7.29 Beta / Developer ROM and MIUI 8 v184.108.40.206 Global Stable ROM. However, if you live in a country that requires a manufacturer of 4G phones need to disable the option unless some rules are met, then you will seriously need this mod.
Simply download the 4G fixer mod package (zip) file from direct link below and flash it through TWRP. Again, TWRP custom recovery needs to be installed on your phone. Do not forget to wipe cache and dalvik cache after flashing the mode package below.
Credits belong to MFajriRamdhani.