Blackout native excel functionality currently only supports excel documents created in Excel 2007 or newer. Blackout makes extensive use of the Office Open XML format and the Open XML SDK provided by Microsoft. Through the use of these standards, we are able to guarantee a high level of performance, stability, and consistency.
All versions greater than Excel 2007 are supported. If you attempt to redact a document using Blackout made in Excel 2005 or earlier on either the Relativity viewer or through an automated Blackout job you will receive a friendly warning indicating that the version is not supported.
Currently, the only available workaround is to convert these documents to the newer Excel format. Doing so is as simple as opening the document with a later version of Excel and re-saving the document using the "Excel Workbook (*.xlsx)" type for the "Save as type:" field.
If you have a large number of documents to convert, please contact your IT team as it is possible to mass convert these documents. In addition, Microsoft also provides tools to automate this process.