Spreadsheet file format problem
A common reason why uploads fail is that the upload file is in the wrong format.
Most people prefer to edit downloaded Code Lists, Contexts and Context Maps in spreadsheet format. CLMS supports this. When you download something from CLMS it arrives in a special XML Spreadsheet format. You can edit it and save it in this format and subsequently upload it without problems.
However, CLMS is unable to accept spreadsheets in the standard Microsoft Office Excel Workbook format. It requires spreadsheets to be saved in XML Spreadsheet format if they are to be uploaded.
When saving spreadsheets some versions of Excel offer to change the format to the latest version of Excel. Don't let it do this - you need to retain the existing format:
If you change the name of the file some versions of Excel will helpfully change the format from XML Spreadsheet to Microsoft Office Excel Workbook. You should change it back again.
Furthermore, some versions will also change the filename by appending ".xml" (as above). You should remove the extra ".xml":
If you only notice that your file has a filename ending in ".xls.xml" having closed Excel you can rename it outside Excel by removing the extra ".xml".