I need to authenticate multiple accounts

I have searched the forum, and it seems like it is possible So I gave it a try, but I failed

I had tried using the same API APP_KEY & APP_SECRET, it failed Both my session return the same access tokens pair

So I try using different API APP_KEY & APP_SECRET, under same Dropbox account, it failed too

So I try again using different API APP_KEY & APP_SECRET from different Dropbox accounts, it still failed

Anyone can provide me a solution? Thanks in advance

Below is my code, mainly comes from the DBroulette example

onCreate (android)

AndroidAuthSession session = buildSession();
mApi = new DropboxAPI<AndroidAuthSession>(session);
AndroidAuthSession session2 = buildSession2();
mApi2 = new DropboxAPI<AndroidAuthSession>(session2);

onResume (android)

AndroidAuthSession session = mApi.getSession();
if (session.isLinked()) {
dbsetLoggedIn(true);
} else {
dbsetLoggedIn(false);
}
if (session.authenticationSuccessful()) {
try {
session.finishAuthentication();
TokenPair tokens = session.getAccessTokenPair();
dbstoreKeys(tokens.key, tokens.secret);
dbsetLoggedIn(true);
statusTv.append("Dropbox authentication successful\n");
} catch (IllegalStateException e) {
Log.i("Dropbox Error", "Error authenticating", e);
}
}

AndroidAuthSession session2 = mApi2.getSession();
if (session2.isLinked()) {
dbsetLoggedIn2(true);
} else {
dbsetLoggedIn2(false);
}
if (session2.authenticationSuccessful()) {
try {
session2.finishAuthentication();
TokenPair tokens = session2.getAccessTokenPair();
dbstoreKeys2(tokens.key, tokens.secret);
dbsetLoggedIn2(true);
statusTv.append("2Dropbox authentication successful\n");
} catch (IllegalStateException e) {
Log.i("Dropbox Error", "Error authenticating", e);
}
}

OTHERS CODES 

private AndroidAuthSession buildSession() {
AppKeyPair appKeyPair = new AppKeyPair(
android dropbox dropbox-api
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