Dead touch screen after replacement (3 diffrent assemblys)

Hello , i replaced 3 lcds (full assembly ) on my lg G2 and none of tham work . the touch screen is dead but the screen works i dont know what could be the issue any more , the connectors are in place and non of tham look bent ,on motherboard or on the screen ... any answers on what could be the issues i am dealing with excluding the faulty digitizers?