[Smush Pro] Smush Pro not working…

Hello,

I have been using Smush Pro and it has worked fins and comprresd more than 15K of pictures now.

But, this evening it stopped working, I cannot even get the plugin to start, this message is displayed:

The site is experiencing technical difficulties. Please check your site admin email inbox for instructions.

I have done nothing else than running smush, so I can't find out what has happened. Any ideas?