[John Mavety]

Thanks for responding. I’m on a MacBook Pro, connected to an external monitor. I’ve worked out that the problem only occurs when the comp window is on the external monitor. When I drag it onto the laptop screen I can control click to select layers. I used to be able to do the same on the external monitor but it stopped working a while back, possibly when I updated the Operating System (to Version 10.13.6). If anyone knows how to get it working across both monitors please let me know. Thanks again.