Unable to login via Facebook (Parse): error code 251

I have an app in the App Store which is using Parse and automatically creates anonymous users (I set [PFUser enableAutomaticUser]). So now I have several thousands of users in a Parse users table.

Now I'm trying to implement full profiles and convert anonymous users to non-anonymous by calling:

[PFFacebookUtils linkUser:currentUser permissions:@[@"public_profile", @"email", @"user_friends"] block:^(BOOL succeeded, NSError *error) {
        if (succeeded) {
            //some logic
        } else {
            NSLog(@"Error: %@", error);
        }
    }];

BTW I've also tried:

        [PFFacebookUtils logInWithPermissions:@[@"public_profile", @"email", @"user_friends"] block:^(PFUser *user, NSError *error) {
        if (!user) {
            NSLog(@"Uh oh. The user cancelled the Facebook login.");                
        } else if (user.isNew) {
            NSLog(@"User signed up through Facebook!");
        } else {
            NSLog(@"User logged in through Facebook!");
        }
    }];

But in both cases I get an error: 251 - The supplied Facebook session token is expired or invalid.

What I've already tried:

• Logout anonymous user


• Refresh session


• Close and re-auth session

Nothing here works for me. Does anyone know what to do in this case? How do I correctly convert anonymous user to non-anonymous?