[Users] Pack for QField greyed out

[Martin Weis]

Hello,

I cannot pack a project for qfield, since the entry is disabled/greyed out.
It may be that I opened a packed one (the project name is set and
contains _qfield) and saved that as qgz.
Export options are OK, as far as I can see (lots of things not going
into export).
Can a certain layer or setting be the culprit?
I currently have created a new project, from where export to qfield is
possible after moving layers into it.

* is it possible to work on with qfield projects in qgis in general?
* Is it possible to get a hint what is blocking export?

Thank you
Martin