EM 13c Agent is unreachable as its first severity has not yet come after blackout end

The agent status shows "Agent Unreachable (Post Blackout)" in Oracle Enterprise Manager 13c console. On the agent home page, it shows following error message,

  Agent is unreachable as its first severity has not yet come after blackout end.

It is seen in EM 13c, can can be fixed by running following commands on agent host,

  ${AGENT_INST_HOME}/bin/emctl stop agent

  ${AGENT_INST_HOME}/bin/emctl  clearstate agent

  ${AGENT_INST_HOME}/bin/emctl start agent