Hey @Sigord! From your description, it sounds like you're doing this:
- Drop-down filter with a year in data source 1
- Year parameter in drop-down filter, 'year'p
- Advanced data source filter in data source 2:
Can you confirm if the parameter is being set to a value when the report is opened? If not, this would cause 'year'p to initially not start off with a value.
Since both data sources share Year, have you tried mapping Year from data source 1 to Year in data source 2? That way you can avoid a parameter-based solution.