Why R syntax cannot be highlighted?

[wsadlxx]

I just want to use R syntax highlight, but nothing happened even though I have changed language to “R”.
Is there anyone who could tell me the the reason?
Thanks~

My Notepad++ edition is 7.5.1 (64bits) on Windows 10 platform.

[MAPJe71]

@wsadlxx see this issue

[wsadlxx]

Aha！
Thank you very much!