Hey there, google reads the css and js scripts in order to define how user friendly your site is, especially when served on mobile devices.
Here is yoast’s take on it:
https://yoast.com/wordpress-robots-txt-example/
Also, take a look at this thread from today, on the same issue.
https://ww.wp.xz.cn/support/topic/googlebot-cannot-access-css-and-js-files
KR
Thomas
Are you using any ad block plug-in? Depending on your GA setup, the script might be loaded through the doubleclick domain, which in some cases is blocked by ad blockers.
KR
Thomas