CSF - cant login

Hi folks.

I installed csf via box install csf

I got the message:

You may now access the CSF UI on https://redacted:3443
Username: redacted
Password: redacted

When I visit the UI page I see the login box, and enter the provided username and password.
On clicking submit the login form just reloads - I can never login.

I’ve tried removing and reinstalling several times (interestingly the installer gives me the same password every time) with the same result.

Any ideas? What further info could I provide to help diagnose?