Thanks for all the replies. I managed to sort it out eventually.
I’m using a MacBook Pro, there was another record button that I couldn’t see because of the small size of the screen. I had to extend the transport control pad out to see it.
I joined an Avid Pro Tools Facebook group to ask for advice. I don't think I’ve ever encountered a nastier, more up themselves group of people in my life. All the sarcastic comments I received.
Anyway, thanks again to all those who offered advice.