My Sony Xperia Z5 won't turn On.

My sony xperia z5 won't turn on ever since it turned blacked out. it happened couple of years ago and it wasn't charging as well so i replaced the battery with new one but it stayed the same. charging won't start neither its charging led gets blinked. i showed it to repairers but no one was able to make it fine. it doesn't show the current when connected with the cable. what could be the problem