how do i address this issue ?
And where do I look to get an information about whats wrong ?
BR Lars
It may help to say the hosting environment, version of ERPNext and how obtained, and the steps taken that lead up to the message appearing.
erpnext 13.x.x-develop
frappe 13.x.x-develop
Ubuntu 18.04
Can you access the site via ssh?
You can look in logs folder and find setup_wizard.log to see what is wrong.
reboot was the solution 