A ping test to the public WAN (which is used to access the vnc server says: 13 packets sent, 100% loss.

Here are the current settings in the pfSense router:

If: WAN
Proto: TCP
Src. addr: *
Src. ports: *
Dest. addr: WAN address
Dest. ports: 5900 (VNC)
NAT IP: 192.168.1.110
NAT Ports: 5900 (VNC)

Remmina on the local client has settings:
Protocol: VNC - Incoming Connection

I installed the nmap package on pfSense and scanned the VNC server IP 192.168.1.110:

Running: /usr/local/bin/nmap  -sS '192.168.1.110'

Starting Nmap 6.47 ( http://nmap.org ) at 2015-10-22 18:10
Nmap scan report for 192.168.1.110
Host is up (0.00011s latency).
Not shown: 998 closed ports
PORT    STATE SERVICE
139/tcp open  netbios-ssn
445/tcp open  microsoft-ds
MAC Address: xx:xx:xx:xx:xx:xx

Nmap done: 1 IP address (1 host up) scanned in 3.55 seconds

On the VNC server I ran a check for ports:

$ netstat -an| grep LISTEN
tcp        0      0 0.0.0.0:139             0.0.0.0:*               LISTEN     
tcp        0      0 127.0.0.1:5939          0.0.0.0:*               LISTEN     
tcp        0      0 127.0.0.1:631           0.0.0.0:*               LISTEN     
tcp        0      0 0.0.0.0:445             0.0.0.0:*               LISTEN     
tcp6       0      0 :::139                  :::*                    LISTEN     
tcp6       0      0 ::1:631                 :::*                    LISTEN     
tcp6       0      0 :::445                  :::*                    LISTEN     
unix  2      [ ACC ]     STREAM     LISTENING     13793    @/tmp/.ICE-unix/1756
unix  2      [ ACC ]     STREAM     LISTENING     13299    /tmp/.X11-unix/X0
unix  2      [ ACC ]     STREAM     LISTENING     11761    @/tmp/dbus-3SWEl6nEWV
unix  2      [ ACC ]     STREAM     LISTENING     13742    /tmp/ssh-sCsM4CtFJXXD/agent.1756
unix  2      [ ACC ]     STREAM     LISTENING     13794    /tmp/.ICE-unix/1756
unix  2      [ ACC ]     STREAM     LISTENING     4339193  socket
unix  2      [ ACC ]     STREAM     LISTENING     4434331  @/dbus-vfs-daemon/socket-WHSe9pJh
unix  2      [ ACC ]     STREAM     LISTENING     13601    /run/user/1000/keyring-Qt4qES/control
unix  2      [ ACC ]     STREAM     LISTENING     13298    @/tmp/.X11-unix/X0
unix  2      [ ACC ]     STREAM     LISTENING     4435395  @/dbus-vfs-daemon/socket-zn9XHULl
unix  2      [ ACC ]     STREAM     LISTENING     59185    /var/run/cups/cups.sock
unix  2      [ ACC ]     STREAM     LISTENING     20084    @/dbus-vfs-daemon/socket-jyfxNG4K
unix  2      [ ACC ]     STREAM     LISTENING     3497359  @/dbus-vfs-daemon/socket-FowUdH6c
unix  2      [ ACC ]     STREAM     LISTENING     19875    @/dbus-vfs-daemon/socket-UU1KLUYI
unix  2      [ ACC ]     STREAM     LISTENING     13755    @/tmp/dbus-GoVnB738xE
unix  2      [ ACC ]     STREAM     LISTENING     10844    /var/run/dbus/system_bus_socket
unix  2      [ ACC ]     STREAM     LISTENING     9672     @/com/ubuntu/upstart
unix  2      [ ACC ]     STREAM     LISTENING     10088    /var/run/sdp
unix  2      [ ACC ]     STREAM     LISTENING     12652    /var/run/acpid.socket
unix  2      [ ACC ]     STREAM     LISTENING     11388    /var/run/samba/nmbd/unexpected
unix  2      [ ACC ]     SEQPACKET  LISTENING     1935     /run/udev/control
unix  2      [ ACC ]     STREAM     LISTENING     19605    @/tmp/dbus-96mDEiIXYs
unix  2      [ ACC ]     STREAM     LISTENING     20085    @/dbus-vfs-daemon/socket-xUgXu05f
unix  2      [ ACC ]     STREAM     LISTENING     10175    /var/run/avahi-daemon/socket
unix  2      [ ACC ]     STREAM     LISTENING     3774006  @/dbus-vfs-daemon/socket-tfPuYBAd
unix  2      [ ACC ]     STREAM     LISTENING     14279    /run/user/1000/pulse/native
unix  2      [ ACC ]     STREAM     LISTENING     24750    /tmp/.com.google.Chrome.sB9dVB/SingletonSocket
unix  2      [ ACC ]     STREAM     LISTENING     13796    /run/user/1000/keyring-Qt4qES/ssh
unix  2      [ ACC ]     STREAM     LISTENING     13798    /run/user/1000/keyring-Qt4qES/gpg
unix  2      [ ACC ]     STREAM     LISTENING     13801    /run/user/1000/keyring-Qt4qES/pkcs11
unix  2      [ ACC ]     STREAM     LISTENING     11497    /var/run/gdm_socket
unix  2      [ ACC ]     STREAM     LISTENING     3477971  @/tmp/dbus-rSkDIWWoq1

Any help to make this work again please?

If you are trying to allow a remote client to connect to your VNC server, you need to change the destination address to WAN address, not LAN and change the port's to match. If you need both RDP and VNC port's NAT'd make two rules with 3389 -> 3389 and 5900 -> 5900.

I also tried:
The LAN local connection works.
The WAN remote connection doesn't work, as per below.

Well, I thought maybe the local client cannot access the remote host, due to TeamViewer running a remote connection.
So, I closed TeamViewer, then Quit TeamViewer, however the same Remmina error:
Remmina connection WANIP:3389. Error: Unable to connect to RDP server WANIP:3389 (comes up instantly)
Remmina connection WANIP:5900. Error: Unable to connect to RDP server WANIP:3389 (comes up after a few minutes)

Okay,
Local client Remmina:
Protocol: VNC - Virtual Network Computing
Server: public WAN IP
User name: blank
Password: blank
Connect:

Remote host Remmina:
Protocol: VNC - Incoming Connection
Listen on Port: 1
User name: blank
Password: blank
Connect: read (9: Bad read descriptor)

vino-preferences: I unticked 'Automatically configure UPnP router to open and forward ports

I think tightvncserver may be running in Terminal, which shows output:

$ tightvncserver

New 'X' desktop is userName:1

Starting applications specified in /home/userName/.vnc/xstartup
Log file is /home/userName/.vnc/userName:1.log

You want to connect from the outside (any where on the net) using any port
to
the IP of your psEnse WAN, using port 3389 (MS RDP).
This connection will be natted to the device /PC on LAN, port number 5900 (VNC).

Building a NAT rule like that (pretty straight forward) will, by default, generate the corresponding firewall rule.