Syntax highlighting doesn't work on some files


I’m viewing XML file generated by an app. Some of them show the syntax highlighting just fine. Others show no highlighting at all. All are .xml files, set with CRLF, UTF-8, XML.
Atom: 1.22.1 x64
MacOS 10.11.6


Can you share any of the files that show no syntax highlighting?

How large are these files?