Some time back I was struggling to get a Parameter working for a SharePoint list.
The report had 2 datasets, and the parameter had to come from the second dataset. Which was a Calculated Feld using a LOOKUP FIELD by the way.
So the BU parameter was a lookup value from the second dataset PROJECTS. So I though just as straightforward a calculated field to the primary dataset and that’s it.
But apparently it a parameter does not accept a calculated field that hold a lookup function
Remove the calculated field from the primary dataset.
Go to the TABLIX Properties and go to FILTERS, and add the Lookup Field expression there to filter the returned items in the list.
It is working well now.