Downloading Santander bank statements in XLS produces the bank statement in HTML coding

Hi Apple Community, I am trying to get my bank statements in an XL format to then convert to CSV files. So I download Santander bank statements, inputting a specific date range 'from' and 'to'. When I select the XLS format, the download appears in the download file in an HTML format with the financial information buried inside it. Santander did have this issue in 2016 but say it was resolved. On opening the file there's a pop up saying 'table data has been imported and can be adjusted' but have no idea what to choose when I click on this or even if this is the right way to correct the issue. Under File, I've tried exporting the download to CSV and Excel but no progress. Can anyone shed light on this? Thank you.