The “cancel” button for Inkscape extensions has _never_ worked; I’m not sure why they have a button there at all.
Please download and install the new version of the EggBot extensions for mac, version 2.6.3, and then restart Inkscape. (Version 2.5.0 has never worked on MacOS 10.11.)
You can find the new version here: https://github.com/evil-mad/EggBot/releases/latest
