This one started after a firmware update.
Until QNAP fixes the firmware do this:
SSH into the nas and change /etc/resolve.conf from ‘nameserver 127.0.1.1’ change ‘127.0.1.1’ to your DNS server. If you are unsure what you dns server is, it is most likely your default gateway if you are a home user. If you still are unsure make it 8.8.8.8
so the file will read:
nameserver 8.8.8.8