There is a freemarker file (ftl) in my IntelliJ project that is incorrectly recognized as a text file. There are many of the same type that are correct. I am aware of the "Mark as text" option. This may be the original reason this file was marked as text but I am not provided with a "mark as ftl file" option to turn it back, if indeed this is the problem. If I mark other ftl files as txt, I am able to turn them back into ftl files as expected.
Please ensure that this file (or a pattern that represents it) is not listed under
Settings → Editor → File Types→ Text files
For OS X
Preferences → Editor → File Types→ Text files