I made a blogpost yesterday about Gemini and in it I showed an issue about Slicers in a PivotTable that kept turning up empty:
Tatyana from Microsoft apperently read about the issue and posted the resolution in a comment:
Go to “regional and language options” in control panel and change current format to English (United States). That should fix slicers issue.
And indeed it did fix the issue, great fast reply from Microsoft: