Few months back I prepared a demo on Fitbit oauth2 public APIs in which I used to log in with a particular user and get his activities. It was working fine. But recently, I opened the demo and tried to log in with the same user but it is not getting logged in and repeatedly giving me this error.
I tried to change the client secret key of this demo app which I registered on Fitbit but nothing happened. I am stuck here.
There is problem with the format of Callback URL. I think Fitbit has recently changed it.
Earlier, the format of Callback URL was "demoapp://" but now it will be "demoapp://something"
Please refer to my answer on other question.
Setting up Fitbit api in xcode Swift