requestPhonePermission() does not working

[youngnoble531]

if (!PermissionsManager.get().isPhoneGranted() && request) {
PermissionsManager.get().requestPhonePermission().subscribe(this);
return false;
}

...

public void call(PermissionsResult permissionsResult) {
    if (android.os.Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
        if (PermissionsManager.get().isPhoneGranted()) {
            TelephonyManager tm = (TelephonyManager) getSystemService(Context.TELEPHONY_SERVICE);
           String imei =  tm.getImei();
        }
    }
}

...

In this case, the call subscribe callback function does not called. It seems the requestPhonePermission() does not working.