Since a windows update I think, essential graphics preview will not show thumbnail or motion preview in the list(Adobe originals and third party ones). I deleted all .mogrt files and replaced them but still not shown preview.
We've been able to replicate the issue and are working on a fix. Thanks so much for bringing it to our attention and providing detailed information.
The workaround in the meantime would be to change your Windows User Account to change the character with the umlaut to a non-special character (a-z 0-9).
We've implemented a fix in 24.2.0 build 77. Please update to the latest beta version of Premiere Pro in the Creative Cloud app and let me know if this does or does not resolve the issue for you.