(As per OpenWRT Wiki that firmware was only tested on MR3020 ver 1.4. What version is your MR3020? Make sure it's the right firmware you use.)
If you want to reinstall the original firmware and you have piratebox running on your router then first you need to stop piratebox service:
after this you should be able to ping google and proceed with the guide.
If you want to reinstall the original firmware and you have piratebox running on your router then first you need to stop piratebox service:
/etc/init.d/piratebox stop
after this you should be able to ping google and proceed with the guide.