If you are using it as Top/Bottom AD, please check Check if used in Top/Bottom Ads from the widget menu. Please refer to our documentation on section 3.7. There are times that Adsense won’t show right away because Adsense is loading. If there’s no AD showing, the CSS ins tag is set to transparent on AD widget, while on script it is set to yellowish color background which may seem that the AD widget is not working, but in reality, both works, it has just a different background color.