Movies in PhotoPaint -- can't start making one.

I've successfully used earlier versions of PhotoPaint for making movie GIFs and AVIs but I've stumbled on a bug in PhotoPaint 2019 (64-bit, Version 21.3.0.755, source 707028) under Win-10.  When I go for File->New, the "Number of frames" widget is grayed out and doesn't accept an input even though both the Movie toolbar and docker are enabled.  Tweaking A Repair operation didn't help.  How can I enable this feature?