This report gives you inside into a variety of automated and non-automated processes running in your store.  You can drill down into them to see what happened with a process and why.  Expand the "Supplier documents importing and processing", find the date(s) that you want to investigate.  Click on the "Show" link to see that detail for any process that ran.

Once you've clicked on the show button review the log and look for the issue.  It may be helpful to use the "Find" feature in your browser to search if the process is long.  If the invoice number that is problematic contains the numbers 1131, as an example then search for it to find an entry relating to that.  

In the screenshot below you can see that an invoice containing that number has an issue.  Either that supplier doesn't exist in the system OR the code RS is not inputted in the vendor's record. - Yellow 

Additionally - you can see that several reorder numbers were not found.  Either the product doesn't exist, OR the reorder number is incorrect. - Green

Edit the Supplier and add any needed information in the Supplier Documents Settings.  As this is a Fintech Supplier, which is centralized, it only needs the File type and Vendor ID.  Non-Fintech suppliers will need all the fields populated.

If the Reorder number was not correct or missing, edit the product and look at the Supplier Details.  Be sure the right Reorder Number and Supplier is set.

Go into the supplier record of the supplier that sends the file.  You will find suppliers by going to Admin and searching for suppliers in the back office, then searching for the supplier in question in the suppliers section.  Scroll down until you see the windows below.  These are all the most recently imported documents.