Have you tried restarting the ePO services on the server?
If that does not work, are you able to hit the yoursite/core/config page and check the database connection?
This link has the directories for the server logs, you could start checking through there also: https://kb.mcafee.com/resources/sites/MCAFEE/content/live/PRODUCT_DOCUMENTATION/ 24000/PD24809/en_US/epo_510_rg_Log%20Files_0-00_en-us.pdf
Yes I have tried to restart the services and even server also but Event Parser service is not starting.
Secondly I tried to open the mysite/core/config and connection is not successful . do I need to put the password or should I try without?
In user password if I click "Change password" then It will change the password on SQL as well??
The event parser service is not necessary to be started to hit the ePO front end. The event parser is just a service that parses the events from the agent to the DB, so seems you might have a DB connection issue.
The un/pw in that core/config page is based on however you have your SQL user setup. Find whatever user you are using for SQL, maybe change its password, then re-input it into the core/config page and test.