Not sure if a firmware update resets everything as usually it maintains settings, data etc.
Try starting the tablet in safe mode and check if the WiFi turns on.
If it does then a downloaded app is the cause of the problem. The trick is to find out which one is the cause
If still no good in safe mode, backup the tablet to a computer and then try a factory data reset and see if this resolves the problem.
If it now works OK restore the tablet with the backup you made earlier and then check again that it still works
If still no good when reset, it may be a hardware problem
Don’t know if this will work but try the WLAN codes to see if there is any response.
Here’s a link to the ifixit Asus MeMO Pad 7 ME170C repair guides which will help you to open the tablet.
I’m assuming that the WLAN/BT IC is hard mounted on the systemboard and is not a separate module attached to the board, so it will be difficult to replace it if it is. Look for the markings on the ICs to help determine which one is the correct IC for the WLAN/BT. You may have to search online using the number printed on the IC to find out what it does.