Why can't I turn on my Samsung S4I9505 wifi ?

[AC Question]

At first I could turn on the Wi-Fi but it took about 1 minute to turn on. A few months later it wouldn't turn on at all. The Wi-Fi button would be grey. I reset the phone a couple of times, turned off Wi-Fi power saving mode, flashed a different rom, changed battery and so on. Is it a motherboard problem or is it the Wi-Fi module?