Title Blocks can't be placed in diagrams

Hello everyone,
I have a problem with placing title blocks in diagrams.

At that time I work with two models in my workspace.
In the first one I can place title blocks in the expected way.
In the second one I can’t. If I select title blocks and place it over any element in my diagrams I have always the “prohibition” and not the “plus” sign.

I have no clue what is wrong here, or if I have deactivate someting that could be necessary for this feature.

Hope someone can help me.
Thanks a lot


Working with Capella 5.2 and with the following Add-Ons:
Diagram Styler
Property Values
HTML Export