MQTT doesn't like static IP address

allow-hotplug wlan0
iface wlan0 inet static
  address 192.168.1.1
  netmask 255.255.255.240
##  14 usable addresses.  (Well 13, as this is one of them)
#  network 192.168.1.0
  network 192.168.0.0

The network value is definitely wrong. The commented out value is the right one.
I don't know how the Raspberry Pi interprets these conflicting values but you might have a misconfigured network interface, so the Arduino probably cannot reach the Raspi.