A family of Microsoft relational database management systems designed for ease of use.
We don't know what you know or do not know about Access. Can you run the report, then click the button in the Ribbon to put it in design view, then inspect the RecordSource property, and other properties such as Filter (all on the Properties window).
If the RecordSource is a query, open that query in design view and inspect it. There may be something on the Criteria line that restricts it to old data.
If none of this yields results, inspect the code in the Button_Click event which I'm assuming you run the report from. DoCmd.OpenReport has an optional argument to provide a Where-clause which can restrict what data you are seeing.
If all of the above is TOTAL GREEK (or GEEK) to you, hire some professional help. Should not take too long to figure out.