Error while setting server report parameters. Error message: The report server has encountered a configuration error. Logon failed for the unattended execution account. (rsServerConfigurationError)

Facing this kind of error when accessing any report:
Error while setting server report parameters. Error message: The report server has encountered a configuration error. Logon failed for the unattended execution account. (rsServerConfigurationError)

Solution:

Go to Reporting Services Configuration Manager-> Execution Account and specify your credentials as per screen shot and happy SSRS.....