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:
'year'n = 'year'p
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.
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