Subsription Metabox Gone

Good morning,

Today we’ve a cancellation to a subscription to our website. Previously there was Metabox showing up in the back-en where we could take care of this. Somehow this metabox isn’t there anymore. Can you please help me out?

Ps. name website is in Dutch, we have a website in English with the same theme and plugins running, at that website everything seems to work just fine.

The page I need help with: [log in to see the link]