When export QuickBooks Profit and Loss by Class report to Excel, a warning message:
Excel allows 256 columns in a worksheet.
This report has 3445 columns (5 row title columns + 3440 data columns)
Use "Customise" to change the number of columns in this report.
This was neither an error nor bugs in QuickBooks. This was a limitation in Microsoft Excel, as the warning message stated; Excel allows only 256 columns in a worksheet.
In this case, this user has more than 3000 data columns which was far beyond Excel can take. To resolve it, you may customise your report to reduce the number of Class to be displayed.