Can't even get the simplest self-made Mogrt (from PR) to work in Rush

Hey guys,

I tried to be as descriptive as possible. I feel lost. Can anybody chime in and tell me, what I'm doing wrong? s. description below.

Thanks, 
Marc

Windows 11, Rush 2.5.0 (build 403), Premiere 22.6.2 (build 2), german

Problems with self-authored Mogrts (PR) - even if it's just one simple text element: 

• Whatever I try, the same Mrgrts installed in the library which appear in Premiere will not be displayed in Rush.
• If I want to use the function "Vorlage installieren" (may translate into "install template") and choose a mogrt-file I get the error message "Wir konnten diese Grafik nicht in Ihrer Bibliothek speichern." -> "We could not save this graphic to your library." with no additional error code.

What works, though: 

• make Mogrt with AE, put it into library, use it in Premiere
• make Mogrt with Premieren, put it into library, use it in Premiere
• use the templates from adobe that come with Rush

What I am aware of:

• Rush doesnot support Mogrts from AE, so I use PR-Mogrts for testing
• I have the latest versions of each of the applications
• I tried it already on 2 different computers 
• I checked all the docs I could find