Hi Gill,
I was having the same issue and even did a reinstall before I realized that the problem was not the install or even the version. Vue 6.60-04 Build 292711 in my case. If you use a custom interface for some reason the option is not there, so I chose to use the Vue 5 interface and after restrarting Vue the option to zoom was back.
Hope this not a repeat of someones  reply.
Hope all is well with you Gill my friend.
regards, Tom