SiteOrigin Page Builder tab says undefined

Siteorigin Pagebuilder seems to have fallen over. I am using WP 4.5 with Kadence Virtue theme.

My site is here: https://13.79.166.215

When I try to edit the hompage, the pagebuilder tab says, ‘undefined’. I can click on it but none of my widgets are present.

Any ideas what is the matter?