Including ConvertFlow with require.js
Magneto 2 uses require.js. Require.js is a javascript library manager, and it will throw errors when javascript libraries like ConvertFlow are loaded into the page without require.js because it considers the library unapproved.
To have require.js approve of ConvertFlow, you'll need to have ConvertFlow loaded through require.js' library inclusion functionality. You can copy your ConvertFlow website's script path from the install page, like so:
Enabling Google Fonts in require.js
ConvertFlow also loads in Google Fonts using the WebFont library. If you don't already have WebFont installed on your website, you'll need to add the following script source to your require.js inclusion list.
https://ajax.googleapis.com/ajax/libs/webfont/1.6.26/webfont.js