@monecchi Please check if the mysql-root-user is enabled for remote hosts access. You need to check the mysql.user table
SELECT user, host FROM mysql.user;
If not then you can enable remote host access for the mysql-root-user and then check again.
CREATE USER 'DBuser'@'%' IDENTIFIED BY 'DBpassword';
GRANT ALL PRIVILEGES ON *.* TO 'DBuser'@'%' WITH GRANT OPTION;