Import-PWDocumentsBySpreadsheet ignoring Attribute update

I have looked at the other questions and answers around this cmdlet but can't see much in the way of resolutions, they all seem to be taken offline to email conversations.

I am trying to use this cmdlet and have generated the spreadsheet using the Export-PWDocuments with the -ExportMetadata on.

I have added new documents to the existing spreadsheet and added my files to the same location that the sample file was exported to.

I am then using Import-PWDocumentsBySpreadsheet to bring the original file, with modified attributes, and 5 new files in with attributes.

The files are imported, but the attributes are not populated, and the existing file's attributes have not been updated.

I tried a second time, with all files already existing in ProjectWise, using the -OnlyUpdateAttributes switch, but nothing has been updated.

The process seems to be ignoring the Custom environment tab in the spreadsheet, created by the Export-PWDocuments process.

Running interactively I can see the following;

VERBOSE: Selecting attributes with 'ProjectWisePath = '[Path to my file in ProjectWise]' and ProjectWiseDocumentVersion is null'

VERBOSE: Found 0 rows.

This occurs for each file in my spreadsheet, The ProjectWisePath columns in both worksheets are identically populated, so I am not sure why I am seeing the "Found 0 rows" message.

Any help on this would be appreciated.