SSRS only displaying first row

I have a very basic report in SSRS that displays a grid of data. Th开发者_StackOverflow社区e query correctly returns multiple rows but the report only displays the first row. The query is as simple as SELECT * FROM... I dont have any special formatting and the tablix is in the details part of the report, not header or footer by accident. What else can I check?

The tablix was missing a row group.

A similar issue is driving me nuts. I created a report manually from scratch in VS2012, threw a tablix on it and added the columns returned by a simple select. The report preview returns only the first group by primary key. Then I created a similar report using a wizard and that report, although having only cosmetic differences, returns all groups by primary key.