Unifi USG - cannot connect from controller. At wits end.

Bought a second hand usg, a new switch and AP. All good.

Current setup, in total.

Mac connected to USG lan 1 port. USG wan connected to ONT.

I CAN connect to usg at 192.168.1.1 with user/pass ubnt/ubnt. I have configured it for internet.

I can see "congrats, gateway connected to internet". This seems all ok.

I can run the Unifi controller app. It works. I click "launch a browser to manage the network"

It loads a login screen at localhost:8443 with username and password fields.

No username or password will work. Have tried and tried. Forgot password button does not result in a password reset email. What do I do now?

TIA

Cheers,

Joseph