On occasions, a file that is being uploaded to Donorfy may present the error message Unable to open file... File may not be a valid Excel workbook, for example:

The spreadsheet contents and name extension are all appearing to be fine, but the error is presenting as not an Excel Workbook. This may be because there is some hidden formatting that you can not spot from visually looking at the datasheet - often when data is copied from one source to another it can pick up background formatting which then can affect the way in which Excel works with other software. 

To resolve this,

• Open your Excel workbook
• Copy all the data in the workbook
• Create a brand new Excel workbook
• Next, use the Paste As Values option to insert the copied data into the new workbook sheet. This strips out any hidden formatting. 
  
• Set any Date fields to Short Date (dd/mm/yyyy)
• Rename your sheet tab as required (this step is important as will determine which upload process the FileUploader will use)
• Next, Save As
• And then upload to Donorfy

The new file will then upload without presenting the error message.