Problem adding already setup Hub on new phone

I have an old SmartThings Hub, model STH-ETH-001. It has been working fine for years, but I went to add a new device and ran into trouble. Since the last time I used my Smart Things Classic app, i changed phones. Once I logged in on the ST app my hub did not appear. When I try to add tbe hub, it asks for the welcome code which I’ve long since discarded. However, since the hub is already setup and working, why should I need a welcome code, shouldn’t the app just find my hub on the local Wifi network (yes my phone and ST hub are on the same SSID)?

Any ideas?

Click on new user when you login, not existing user.

Also, the code may be on the inside of the battery compartment.