Hi Long,
I think I found the issue. I'm using WPVivid plugin to create a staging site. The staging website has the same setup as the main website, so the same plugins. If I install a fresh WordPresss instance and only add the WPVivid plugin, you will only see that in the staging website. So there shouldn't be anything different form a clean WordPress install.
However, when I install MB views on the staging website, it doesn't show the custom fields (after I set those up ofcourse). But when I do the same on the main website, it does show the custom fields.
So it has something to do with the staging website I've created via WPVivid, but what I don't know. I'm using the same database as the main website, as this is recommended. See: https://wpvivid.com/wpvivid-backup-pro-create-staging-site
Do you know what it could be?
And do you know what I could otherwise do? I'm creating a staging site so I can develop the website. If I can't use it with Metabox, I need to find another solution to safely develop a website while leaving the production website untouched.
Kind regards, Henri