ACR doesn't transfer changes made by masks in ACR on a DNG to PS.

I am using a DNG file for the first time in ACR. I have created changes using brush masks in ACR which disappear when I use Open to take the amended DNG into PS. I can find no way of transfering the changes made into. Reopening the DNG in ACR shows the masks and the subsequent changes.

I have also used the ACR save function and the resultant image doesn't have my changes. 

Am I doing something wrong or is it a bug?