Help, 'morph' disappeared from my transitions pane

[judithvg]

Since a few days now the morph option does no longer appear in my transitions pane. So I cannot apply it anymore in existing or new presentations.
Same pc though, and same PPT version I have been working with all along.

The morphed slides that I made before in existing presentations are still shown as morph transitions, they are not being replaced with fade transitions as in earlier PPT versions, but I cannot add any new morph transitions.

I'm using this workaround now: when I need a morph transition, I copy a morphed slide from a previous presentation and replace the slide contents. But obviously this is not very efficient.

Does anyone have a clue on where my morph transition button might be hiding?

Thanks!
Judith.