In my case, there was an error in log:

190122 4:39:09 [Warning] mysql.user table is not updated to new password format; Disabling new password usage until mysql_fix_privilege_tables is run

The mysql_fix_privilege_tables was replaced with mysql_upgrade in Mysql 5.1. For my Mariadb 5.5 I ran to fix it:

mysql_upgrade --force

And restarted the service.

In my case, there was an error in log:

190122 4:39:09 [Warning] mysql.user table is not updated to new password format; Disabling new password usage until mysql_fix_privilege_tables is run

The mysql_fix_privilege_tables was replaced with mysql_upgrade in MySQL 5.1. 
For my Mariadb 5.5 I ran to fix it:

mysql_upgrade --force

And restarted the service.