I used these two sites as guidance: http://www.wpexplorer.com/quick-guide-wordpress-multisite-installation/ https://codex.wordpress.org/Create_A_Network
Original site was example.com After change to multisite it seems to work.
I added a new site test as test.example.com The new site shows Maintenance.
If I go to Network Admin - Sites, I see the site test.example.com I can Edit it, but I cannot visit the Dashboard nor Visit the site.
What do I miss?