When Document Matching fails before or during a run, Blast Audit usually tells you exactly what is wrong. This article maps the most common add-in errors to the fix that matches the actual UI.
Who this is for
Excel add-in users blocked in
Document MatchingTeam leads troubleshooting workbook setup problems
Anyone seeing engine, header, or output-column errors
Before you begin
You may still see
Copilot Auditin a few older labels.Work from the add-in page
Document Matching.If you applied a template, note which template you used.
Save the workbook before testing fixes.
How to do it
If the local engine is still loading, wait and retry.
If you see The local matching engine is still loading. Please try again in a few seconds., give the add-in a moment and click Run Matching again.
If the local engine is unavailable, reload the session.
If you see The local matching engine is unavailable. or a similar engine-load failure, close and reopen the add-in first.
If the same message appears in every workbook, restart Excel and try again.
Fix duplicate cleaned headers.
If you see Multiple columns share the same name after cleaning: ..., rename the worksheet headers so each mapped column is unique.
Differences like case, extra spaces, or punctuation may still collapse to the same cleaned name.
Fix missing output columns.
If Blast Audit says Select at least one output column before running., go to Finalize your document match and assign at least one Output Columns target.
Fix output range overflow.
If you see Selected range is too far right to create output columns. Excel supports up to column XFD. Move your selection left or reduce its width., move your selected input range left or map fewer output columns.
Recheck template application.
If a saved template does not fit the current sheet, you may see Header mismatch for: followed by column names.
Update the worksheet headers to match the template, or start a fresh setup with Start new document matching.
Run one clean test.
Use a small worksheet range and a small document set.
If that works, the engine is fine and the remaining issue is workbook setup.
Expected result
The error clears before the run starts
Blast Audit moves from
Processing documents...into row matching and output writingHeaders stay unique and outputs write to the intended columns
Avoid this
Applying an old template to a different worksheet layout
Using headers that only look different to humans, not after cleanup
Mapping outputs too far to the right edge of Excel
Clicking
Run Matchingbefore the local engine finishes loading
If it still doesn't work
Test the same setup in a new worksheet with a few sample rows
Note whether the failure happens in one workbook or every workbook
Capture the exact message line from the add-in
If the problem persists after a full Excel restart, send a support escalation packet with the workbook context and error text
Read next
Map Columns Without Errors
Save and Reuse Matching Templates
Run First Document Matching
Fix "No Matches" or Low Confidence
Handle Skipped Documents and OCR Risk
Build a Support Escalation Packet