how to login again

Hi,
How to log in again when I came back to my app without providing username and password again?

at first time when I ran the app, I logged in with stayLoggedIn set to true and when I came back again, I tried:

BackendlessUser Backendless.UserService.CurrentUser() — this one gives null

but

Backendless.UserService.loggedInUser() — this one gives the user object Id from which i can tell the user info I used last time is correct

my problem is: when I try to save any data, I can’t because the user is not logged in

now what should I do to log in again without the need to provide user name and password again

Thanks,
Mohammed

Please ignore, I figured it out