SQLSTATE[HY000] [1045] Access denied for user 'oc_admin'@'172.18.0.1' (using password: YES)

The solution seams to be:

Here adapted for DSM 6.2

sudo /usr/local/mariadb10/bin/mysql --user=root --password=sadKS3f_z5sif nextcloud
create database nextcloud;
create user nxtcloudadmin@localhost identified by ‘admin123’;
grant all privileges on nextcloud.* to nxtcloudadmin@localhost identified by ‘admin123’;
flush privileges;
exit;

sudo nano /etc/mysql/my.cnf

add these lines at the bottom:

log-bin = /var/log/mysql/mariadb-bin
log-bin-index = /var/log/mysql/mariadb-bin.index
binlog_format = mixed

sudo mkdir /var/log/mysql/
sudo chmod 777 /var/log/mysql/

Goes tu packet center, search mariadb stop and restart.

Then try the wizard again where you use:
Username: skycorp
Password: skycorp_password
Database user: nxtcloudadmin
Database password: admin123
Database name: nextcloud
Database host: localhost

And don’t forget to change admin123 into a real password.

regards