Thanks for the advice.
The fan is not working. We followed your advice and tuned the print and set the fan to 100%. The fans didn't work. So then we jiggled the electrical cables gently that are next to the pla tube. If we pushed these away from the pla tube the fans would work. But then they stopped, so I'm assuming it is a loose wire.
I don't know what you mean when you say to "slide up the plastic sleeving at the top of the print head"? Is tghis the black mesh that surrounds the wires?
Thanks for your help and patience.