Multisite and WPMU DEV dashboard disappeared after last WordPress update

Hello there, another problem emerged here.

After the latest WordPress update, the Multisite features and WPMU DEV dashboard disappeared. Re-installing the dashboard doesn't work, I only get a message that the WPMU DEV dashboard still is in this. Perhaps it is, but for me as superadmin its not visible anymore.

Next to this, the whole Multisite constellation vanished.

It concerns

Many thanks