MQTT doesn't like static IP address

From the RPI config files:

/etc/network/interfaces:

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

/etc/dhcpcd.conf

interface eth0
inform 192.168.0.99/24
static routers=192.168.0.254/24
static domain_name_servers=192.168.0.254/24
static domain_search=192.168.0.254/24

static routers=192.168.0.254

denyinterfaces wlan0

/etc/hostpad/hostapd.conf

cat hostapd/hostapd.conf 
interface=wlan0
driver=nl80211
ssid=PiNet
hw_mode=g
channel=7
wmm_enabled=0
macaddr_acl=0
auth_algs=1
ignore_broadcast_ssid=0
wpa=2
wpa_passphrase=************
wpa_key_mgmt=WPA-PSK
wpa_pairwise=TKIP
rsn_pairwise=CCMP

The wpa_supplicant file is nothing special.

This is getting a bit more "Ras Pi" than Arduino.

But that is what is on the RPI.

I have (from the other thread) a ping test and when I connect the Arduino, it only connects one IP address.
via DHCP it is 7. Via static it is 2.
via DHCP the MQTT works. I get messages coming through and I can send messages to the board. All good.
via static, it pings. But MQTT just won't have a bar of it.

Anything else needed?