re-try notification subscriptions if they fail

                if (cnb.open(context)) {

                    for (String account : accounts) {

                        try {

                            cnb.subscribeToGroup(senderId, account, account);

                            accounts.add(account);

                            if (cnb.subscribeToGroup(senderId, account, account)) {

                                existingAccounts.add(account);

                            }

                        } catch (IOException e) {

                            // Try again, next time the account triggers and alert.

                        }

                    }

                    cnb.close();

                    prefs.edit()

                    .putStringSet(ACCOUNT_KEY, accounts)

                    .putStringSet(ACCOUNT_KEY, existingAccounts)

                    .commit();

                }

                return null;