I can't able to create tasks in task center using API

I can able to CRUD operate on Projects, Lists without any error

I can able to fetch tasks in projects and list
but unable to create a task and edit an existing task

if I follow the PUT method to create a task in a list mentioned in the documentation it throws error like below:

{
  "status": 405,

  "statusReason": "Method Not Allowed",

  "message": "Not allowed",

  "toe": "LETFL93CG3-V296V-J574C"

}

If I use POST method for task creation, i get error like below:

{
  "status": 500,

  "statusReason": "Internal Server Error",

  "message": "Internal Server Error",

  "toe": "UJU26ERK38-F78QO-PIQ5O"

} 

PS: if you are wondering about access token…generated using client ID and Secret valid for an hour and the documentation link