iPhone 8 Plus WiFi won’t turn on and Bluetooth won’t turn on

If it affects both Bluetooth and Wi-Fi most likely its a hardware failure of the radio chip that manages both Wi-Fi and Bluetooth. You can try restoring the phone to factory settings to eliminate the possibility of a software issue by following these instructions-->Restore your iPhone, iPad, or iPod to factory settings - Apple Support. If that does not resolve the problem make a Genius Bar appointment at your nearest Apple store-->Genius Bar Reservation and Apple Support Options - Apple

Do you have Wi-Fi in your home?

What error messages have you.