I have a file in 2003 xml format that Excel happily accepts but LibreOffice gives a General error when it tries to open it.
Following a response, I have isolated the problem to a long string in a ss:Data entity. The file is attached (with some style definitions removed).
What is your operating system and version and what is your LibreOffice version (menu Help | About). If it is an old version I suggest to install new version from https://www.libreoffice.org/download
Can you attach the file to this forum? (Note: this file will become public, so if there are some sensitive info in it then don’t send).
Can you also attach the print screen of error message?
Are you opening the file from local disk or from some remote shared directory?
You can also report a bug to bug tracker. The easiest way is to open LibreOffice and from Help | Send Feedback report a bug (you will need to register to bug tracker if not registered yet).