If you can't turn on wifi at all. Most likely the Wi-Fi IC needs to replaced. Not easily replaceable as it requires careful heating to a certain temperature to remove and replace. Better to take it to a phone repair shop that does this.
None of the flex cables that plug into the logic board would cause this.
This can be fixable by flashing system firmware and doing a wipe data / factory reset. If this doesn't work then it's definitely an hardware issue like I said above.
Steps to Factory Reset Samsung Tablet (You will lose all data on the tablet):
- Turn tablet off
- After that Boot your device into Recovery Mode. You can do this by holding the Volume Up + Home + Power keys. When the Samsung Logo pops up, stop holding the power button but keep holding the rest.
- Once your android device is in Recovery Mode, Go to the “wipe data/factory reset” option and select it.
- After that go back to the recovery main menu and reboot the device by “reboot system now” option.