Admin status page reloads

I have access to the admin page https://collab.example.com/browser/dist/admin/admin.html but it refreshes to a popup reading “De server is gestopt; laad de pagina a.u.b. opnieuw.”

How do I successfully access the admin page?

btw I get a 404 on wss://collab.example.com/cool/adminws called from admin-bundle.js#113