Hey.
Zen Unwrap has never functioned the way you described, nor was it designed for that specific workflow. The behavior you experienced previously was actually an unintended side effect rather than standard functionality.
The core purpose of Zen Unwrap is to automatically generate UV islands and sharp edges the moment you select polygons or edges. In the current version, the Mark option was removed because the tool cannot function properly without perfect synchronization between seams and island division.
Looking at your specific workflow, you don't actually need to use Zen Unwrap at all. Once all your seams are marked, simply using the native Blender Unwrap operator will give you the results you need. (Unless, of course, you just prefer using it via the Pie Menu for convenience).
However, if you still want Zen Unwrap to work the way you intend, you can use this workaround:
1. Mark your seams.
2. Make sure nothing is selected.
3. Run Zen Unwrap.
https://zenmastersteam.github.io/Zen-UV/latest/unwrap/#the-behavior-of-the-operator-if-nothing-is-selected