Linked cells do not update between sheets

Linked cells do not update between sheets

I have a master sheet on which I update data and various views of that data on other sheets. Each cell is linked back to the master using the =Master.A2 formula for example. However, when I update any data on the master sheet the cells on the other sheets that reference it are not updated automatically which they should be. How do I ensure that they do update automatically?
Rob