No tweets appear

I can’t seem to get you plugin working. Neither the widget nor a shortcode will display any tweet, independent from the username I try. Most probably, I’m doing something wrong and I’ll feel really stupid when you point it out…

The site in question is https://bakabaka.nl/preview/lexis/. I’ve deactivated all other plugins to prevent any conflicts, but to no avail.

https://www.ads-software.com/extend/plugins/mini-twitter-feed/