Google Analytics Access denied crawl error

I got an email from Google Analytics that Googlebot couldn’t crawl my site.

Here is the error:

Googlebot couldn’t crawl your URL because your server either requires authentication to access the page, or it is blocking Googlebot from accessing your site.

The folder causing the error is: /wp-content/sp-resources/forum-smilies

This is a folder for the plugin Simple Press, forums I am currently using. I’ve contacted them, and they’re saying I need a robot.txt file, but research tells me that WordPress already has a virtual one?

Please advise, thanks! ??