External links hiding in charts — find and remove them
You ran Break Links, maybe more than once, and the warning came back. That's because a chart on one of your sheets is still holding its own reference to another workbook — completely separate from the links Excel's Edit Links dialog manages for formulas.
Why Break Links didn't fix it
Break Links converts external cell formulas to their last calculated values. It does not touch charts. A chart's underlying series formula is a separate object from any cell formula, and Excel stores it independently — so if the chart's data source was ever another workbook, that reference survives Break Links untouched.
How to spot it
Click directly on a data series inside the chart (not the chart border) and look at the formula bar. A normal series formula reads something like =SERIES(Sheet1!$B$1,Sheet1!$A$2:$A$10,Sheet1!$B$2:$B$10,1) — everything local. If instead you see a workbook name in square brackets, e.g. =SERIES(Sheet1!$B$1,[SourceData.xlsx]Sheet1!$A$2:$A$10,...), that series is still wired to an external file, and Excel keeps prompting to update or warning about broken links even though nothing in your worksheet cells refers to it.
How this usually happens
It's almost always a copy-paste: someone built the chart in a working file, then copied the finished chart (not the data) into the report workbook. Excel preserves the chart's original data range references exactly as they were, pointing back at the file where it was born, rather than automatically re-mapping to your local data.
Fixing it
Right-click the chart → Select Data, then edit each series to point at ranges inside your own workbook, or delete and rebuild the chart from local data. Upload your file below first — it lists every chart series with an external reference so you know exactly which charts to fix before you start clicking through Select Data one series at a time.