Just installed new client, opened/synced, added an existing account using my private key from my NEM Stake account, new account activated with correct Public Key and Address but showing zero balance
The status locked just means you are not harvesting on that account. You need 1000 XEM in vested balance to do so. And you have to initiate harvesting from within the account. If you do local harvesting it will be the account you are using, if you do delegated harvesting it will be the proxy account that you give your importance to.