On your server, you should find a folder in wp-content/themes called “generatepress”.
You want to upload your unzipped “generatepress” folder into this folder, overwriting the contents.
Of course, as I’ve explained, there was nothing in this update that would cause the issue to happen, so I don’t have much faith that doing this will make any difference.
One thing you can try is switching to a default WordPress theme like Twenty Sixteen and seeing if the widgets appear. If they do, then we know there’s something in GP we have to look at.
However, when I viewed your website, I could see the widgets without any issue, so I’m assuming it’s something locally on your computer. Have you asked any friends/family members to take a look on their computers?