Due to a change in Meta Box 4.7 with "attributes" param, the old code for Group doesn't work. I've just updated the extension to make it work with new version of Meta Box. Please update.
We have re-downloaded the meta box group plugin along with meta box 4.7.1 and all seems to be working now.
Just a note though that the meta box auto updater didn't pick up that a new version was available for this plugin and https://metabox.io/plugins/meta-box-group/ still shows 1.0.2 as the latest available version. 🙂