Refresh Token Error

[LumiProj]

Hi,

I am using this library its simple and easy I have integrated very well but the issue is when token expired and I am try to call the refresh token. I am getting following error in responce.

Please help me out to resolve this problem.

{"errors":[{"errorType":"invalid_grant","message":"Refresh token invalid:------. Visit https://dev.fitbit.com/docs/oauth2 for more information on the Fitbit Web API authorization process."}],"success":false}