API can´t connect

Hi,
I installed the plugin, no other compression plugin activated. I got an API key and pasted it into the field “Already have an account?”, when I click “save” it tries to connect, but then I get the notice “Something went wrong, try again soon”.
I reinstalled the plugin, restarted the browser, emptied cache, no ide what else could work.

The page I need help with: [log in to see the link]