Hi Thune,
I have released a new version update to this plugin that will solve your issue. Here is what you should do.
1) Remove the plugin.
2) Download the new version of the plugin (1.1) and activate the plugin.
3) In your WordPress Admin Area go to: Settings > Google Fonts and click the Advanced Tab
4) Click the Save Google API Key button.
This plugin uses transients to store all of the google fonts locally so that it doesn’t impact the speed performance of your website. It looks like google returned a temporary error when the plugin queried the fonts and stored this locally instead. This update allows you to refresh the transient by clicking that button instead of waiting for it to refresh every two weeks.