DATABASE ERROR: CONNECTION FAILED! when login to roundcube

issue: when login to webmail via RoundCube getting this error

=====================
DATABASE ERROR: CONNECTION FAILED!

Unable to connect to the database!
Please contact your server-administrator.
=====================

solution:
Try the following proceedures.
>> Repairing the database 'roundcube'.
>>  Running the command /usr/local/cpanel/bin/update-roundcube --force will also help
>>  Last try /scripts/upcp --force