Long-press to show watchface/widgets in app no longer works?

I noticed recently that I can no longer long-press (tap and hold) the screen on my Vivoactive and get the watchface (and built-in widgets) while using an app. (I think this behaviour is/was also available on a long-press of the Down button on non-touchscreen watches.)

Has anyone else noticed this? Is it related to a firmware update, or to apps using a later version of the SDK?

Thanks, Marcus