Getting error while creating group or host

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I have installed ansible tower on CentOS 7. I am getting error message while I am creating host or group. Please advice.

Ansible Version :ansible 2.4.0.0

CentOS : CentOS Linux release 7.4.1708 (Core)

Error message when creating group : Call to /api/v2/Groups/ .Get returned: 500 A server error has occurred.

Error message when creating host: Call to /api/v2/hosts/ .Get returned: 500 A server error has occurred.

Please see below screen shots