[Observium] can't resolve host, but I can ping it

./add_device.php 1.2.3.4 catalyst v1

fails with

Try to add 1.2.3.4: Could not resolve 1.2.3.4. Devices failed: 1.

but ping works

fping 1.2.3.4 1.2.3.4. is alive

but snmpwalk works like:

snmpwalk -v 1 -c catalyst 1.2.3.4 iso.3.6.1.2.1.1.1.0 = STRING: "Cisco IOS Software, Catalyst… ...

The web interface add device also fails same way. what am I missing?