you dont have that issue on your demo because you don’t have the same Link,
this is your link for fonts on demo,
<link rel=”stylesheet” id=”amp-wp-google-fonts-css” href=”https://fonts.googleapis.com/css?family=Karla%7CNoto+Sans%3A700%7COverpass+Mono” type=”text/css” media=”all”>
and this one is mine,
<link rel=’stylesheet’ id=’amp-wp-google-fonts-css’ href=’https://fonts.googleapis.com/css’ type=’text/css’ media=’all’ />,
i would like to use roboto, but how do i change the code from the plugin for font? can i change it from the plugin file directory?