how to get ride of 403 Forbidden nginx when submiting a comment?

I check the file and folder permission files set to 644 and folder set to 755, I deactivate all the plugins. I don’t use control panel and don’ t use apache server I don’ t have .htaccess file because its for apache, then I don’t need to check it.
by all the above solution I still get the 403 Forbidden nginx when adding a new comment!, I don’t know how to fix it!