MaxScale login as root or other users
I asked same question in stackoverflow. It trun out the problem was from maxscale user permissions.

GRANT SELECT ON mysql.user TO 'maxscale'@'maxscalehost';
GRANT SELECT ON mysql.db TO 'maxscale'@'maxscalehost';
GRANT SELECT ON mysql.tables_priv TO 'maxscale'@'maxscalehost';
GRANT SELECT ON mysql.roles_mapping TO 'maxscale'@'maxscalehost';
GRANT SHOW DATABASES ON *.* TO 'maxscale'@'maxscalehost';


https://stackoverflow.com/a/59540995/5456910