StumbleUpon button is not working

Hi, Love your plugin!!!
Lately the StumbeUpon button stopped working. (on all my browsers)
A lightbox opens up but doesn’t load anything.
Tried to remove this button, save, and add it again. But the problem remains.

This is my blog:
http://www.wdb.injoystudio.com

Thank you in advance.

https://wordpress.org/plugins/simple-share-buttons-adder/