Why will Citrix Receiver not go full screen on Samsung Dex?

[RichBroadfield]

It has worked flawlessly for the last 18 months, but in the last week, it now doesn't go proper full screen, and the Dex taskbar remains, as do the window buttons on top bar (min/max/close).

Any ideas? Not sure what's changed, or where i can change that

Thanks for any advice!