The uploader can produce the following error messages, below I try to give some insight on what may cause them and how to resolve the problems.
This means that a file referred to in the Identifier
column of the spreadsheet
template wasn't found on the local filesystem. Make sure that the file exists
and is in the same directory as the tracker sheet.
This means that the group referred to in the Group Name
column wasn't found
in Figshare. Check the spelling of the group name.
This means that some of the categories defined in the Categories
column were
not found in Figshare. Check the categories defined in this column match the
results from the Categories API.
This indicates that Figshare's side refused to create the article. The exact cause of this depends on the detailed message text. The usual reason is that some field failed Figshare's server-side validation. For instance, perhaps your String field exceeded the length limits that are defined in Figshare's administration panel for custom fields.
Any other errors probably indicate a bug in the program. Please contact me directly or raise an issue on the bug tracker.