Found and fixed an annoying intellij bug recently.
This is because the plugins for inspecting those files were disabled when you first load the project. Intellij will assign those file types to be treated as plain text. Then when you turn on the jsp and js inspection plugins, Intellij will not go back and associate the plugin with these industry standard file types/file extensions. (That’s a bug in my book.)
However, you can go in and fix this yourself:
Settings > File Types > Java Server Page files > Add *.jsp
Ditto for any other files that have lost their syntax highlighting, even though the appropriate plugin has been enabled.