Oneplus2 Android phone wi fi issue HELP!!

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l've been searching hundred of forums and sites and l haven't found a fix for this so l though why not just ask here. Nothing to lose and somebody might have had the same issue and found a fix. l've got the OnePlus2 with the factory Oxygen OS that's running on Android's Marshmellow (l've really got no idea what that means btw) For a few days now l don't seem to be detecting any WiFi networks. The problem is definitely in the phone as it doesn't detect wifi anywhere and l'm conecting to the router on my laptop anyway. If anyone knows a fix to this please help ASAP