Doesn't work (Linux Mint, Streamcontroller 1.5.0-beta.11)

Heya! The plugin unfortunately doesn't work at all on my system; 

I have a few GET request URL's that work fine when used in other applications or when pasted into a browser, but using the plugin action on a Streamcontroller button doesn't do anything. The action itself should be configured correctly (URL doesn't need any header or JSON keys in other apps either).