Usually a result of one or more of the McAfee services not running on the ePO server.
McAfee ePolicy Orchestrator 4.X.X Application Server
McAfee ePolicy Orchestrator 4.X.X Event Parser
McAfee ePolicy Orchestrator 4.X.X Server
and database service
SQL Server (EPOSERVER)
are all in a running state
Mark the red text with your mouse and drag it all the way down. In the very end of the text, you will see the actual error description. It is possible that the database is not accessible to ePO at the moment, that is what I usually see. I have set the ePO services to delay their start in order for the SQL services to come up before ePO attempts to connect to the database.
With these errors please refer to McAfee support article:
KB51670 - Unable to log on to the ePO 4.x console (Troubleshooting - Master Article)
What you have looks an exact match to KB69850.
As everyone is suggesting, most common cause for this is Sql connection failure somewhere along the line.
Often an unexpected Sql password change.