Openapi3.0 migration issue

I have upgraded my api from swagger 2.0 to 3.0 and all GET endpoint works fine but when i tried with PUT/POST then it throws an error like below - 

{
"detail": "The server encountered an internal error and was unable to complete your request. Either the server is overloaded or there is an error in the application.",
"status": 500,
"title": "Internal Server Error",
"type": "about:blank"
}

I am using connexion:2.2.0 and Flask:1.0.2 version.

Any suggestion please?