If your tesla account has disconnected for any reason (perhaps because you changed your password), you can reconnect it at any time.
Firstly, once logged in to your ev.energy app, head to the Account page on the bottom left. On the account page, tap on car details at the top. Then click on the status of the car (e.g. Connected or Disconnected) in the second row. Finally, accept the permissions request and you will then be prompted to enter your Tesla login credentials.