How to create a raid on Owncloud already working?

Again good morning,
I uninstalled Owncloud and then again, tried to follow this tutorial https://dietpi.com/docs/software/cloud/#owncloud to re-install it.
After some obvious “DB already exists”, I arrived at the end without any other difficulties.
Now if I give this command sudo ls /mnt/ownclouddrive the output is:

crash-2022-03-01.log		     lost+found
dietpi-owncloud-database-backup.sql  owncloud
dietpi-owncloud-installation-backup  owncloud.log

I assume there are some files in the Owncloud directory… but still trying to reach it through the browser it gives me an HTTP ERROR 599.
Where am I going wrong?