Asus RT-AC87U firmware update - it has internet access but connecting devices do not

Hi - as per the title, I updated firmware and on reboot, other devices connecting to it can't access the internet. DNS seems to work (if I ping a site from my laptop, it resolves, but just get 'Request timed out') whereas the Ping utility on the router pings the same site just fine, and on my backup router, all works perfectly. But the backup doesn't have the parental controls of the AC87U so I want to get it back up and running.

I didn't change any settings prior and nothing is...

Asus RT-AC87U firmware update - it has internet access but connecting devices do not