Unresponsive touch screen

I recently replace the battery. Booted normally, touchscreen works fine then i shutted it down to assemble the back cover and booted again then all of a sudden the touchscreen doesn't respond. What did went wrong? i tried to boot into recovery, cleared the cache partition, done format/recovery and still not responding to touch. Have to use a mouse to navigate. Please help.. i need a solution to this issue. I've sent it to the repair shop and they tested with another LCD but still not responding to touch.
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