Could not connect to the database error

I have setup Matomo in 2 load balancer server, from 1st server it’s working perfectly but from second server sometime it’s working sometimes not.
Getting the following error.

“[localhost] Error in Matomo: Could not connect to the database: SQLSTATE[HY000] [1129] Host '' is blocked because of many connection errors; unblock with 'mysqladmin flush-hosts' This may be a temporary issue, try refreshing the page. Please contact your Matomo administrator if the problem persists.”

Could you please help me on that how to fix the issue?