Refresh token invalid

[SunsetRunner]

Hi-All

We developed two smartphone applications linking step number data using Fitbit's Web API.
So there is a issue, please tell me about two questions.

＊Background
　· We developed two smartphone applications linking step number data using Fitbit's Web API.
　· Authorization Code Grant Flow adopted for OAuth authentication
　· Register and use a separate Fitbit application (ClientID, Client secret separately) for each smartphone application.
　· Cooperate with the separate smartphone applications with the same Fitbit user account.

＊Issue

Executing the access token reacquisition API
with the above two applications installed on one smartphone
failed to reacquire the access token in either or both smartphone applications

＜Response of access token reacquisition API using refresh token＞
HTTPstatus400
 "errorType": "invalid_grant",
 "message": "Refresh token invalid: "Refresh token"

＊What we confirmed
· We confirmed that the refresh token at the time of error occurrence is the same as that at the time of acquisition of the access token.
· No processing is performed to regenerate the refresh token after acquiring the access token.

＊Questions
1.Please tell us the factors that will occur about the above issue.
2.After checking the request header on the authentication login screen, there is a cookie item "oauth_access_token".
  What is this item value used for?
  Since the same value was held by the two applications, please let me check whether there is any influence on the above issue.

[OlegFitbit]

Hi @SunsetRunner,

Thanks for bringing this up. Could you please send me private message with app encoded ids and user accounts you've used to obtain access token, so we could gather more details on your issue.

Thanks,

Oleg 

[hiroko_a]

@OlegFitbitThank you for your confirmation.

"with app encoded ids and user accounts you've used to obtain access token, "

We don't  understand exactly what this means.

What specifically does it point to?