Hi @jayjay94cod
Not sure as your question says "Why won't my wifi turn on?" and then says "..... it never finds the connection? A bit confusing as to what's happening. Does the WiFi turn on but not detect, turns on and then turns off or doesn't turn on at all?
If it does turn on but not detect, try using the phone's WiFi as close as possible to your home network router i.e. <10cm and check if it detects, connects and maintains a stable connection.
If it does it may be an antenna problem - loose connection (either end) or faulty antenna perhaps.
Here's the ifixit [guide|155136] guide that may help.
The WiFi antenna is part of the interconnect flex cable seen being removed in Step.27 (the blue cable being held by the tweezers)
If you suspect that the antenna is faulty, search online for ''(insert full phone model number e.g. SM-S908???) WiFi flex cable'' to find suppliers that suit you best.
If it still doesn't detect when using the WiFi close to the router, then it may be a motherboard problem and further testing using the schematics (I can't find them) would be needed.