Cross authentication of a dropbox user using Access token and secret not happening.

Elaborating my Question: 

1. authenticate the user in my IOS app
2. In Ios app , I retrieve access token and secret from MPOAuthCredentialConcreteStore \*credentials.
3. get the access token from credentials->acccessToken and similarly the secret.
4. Now if I feed these values into another app outside IOS which uses python sdk for dropbox. I get a error message "Invalid token".

But, interestingly the reverse process from step 1 to 4 works. i.e get access token and secret from python SDK and feed it to my IOS app by using 

```
[dbSession updateAccessToken:@"xxxxxxxxx" accessTokenSecret:@"YYYYYYYYYYY" forUserId:@"12345678"];

```

and now i can assess user's dropbox account. Any idea as to whats going wrong? Is there a difference between MPoauth and Oauth? I believe MPoauth is just a wrapper right?

is there any other way to get the access token and secret? 

Thanks for the help.