iOS storing data in keychain for use across devices

I am trying to write data to the iCloud Keychain and have it replicate across devices using the same Apple ID.

If I install an app and call the following code, write an entry, and tun read, I see the data being read back to log on the current device.

However, if I install the same code on another device using same Apple ID, with iCloud/keychain switched on, I don't see the data if I attempt to read from keychain on that device.

I have tried enabling icloud and keychain sharing in capabilities to no avail.

Could someone point me in the right direction please?

-(void)writekc{
    KeychainItemWrapper *keychainItem = [[KeychainItemWrapper alloc] initWithIdentifier:@"AppName" accessGroup:nil];
    [keychainItem setObject:@"password" forKey:(__bridge id)(kSecValueData)];
    [keychainItem setObject:@"username" forKey:(__bridge id)(kSecAttrAccount)];
}

-(void)readkc{
    KeychainItemWrapper *keychainItem = [[KeychainItemWrapper alloc] initWithIdentifier:@"AppName" accessGroup:nil];
    NSString *password = [keychainItem objectForKey:(__bridge id)(kSecValueData)];
    NSString *username = [keychainItem objectForKey:(__bridge id)(kSecAttrAccount)];
    NSLog(@"Password:%@, User:%@",password,username);
 }

In the end I have used SSKeyChain which has sync capability built in.