Under “The issue you are facing” I would expect a precise description about what you are doing, what is expected to happen, and what happens.
What do you mean by “can’t log on”?
In my installation I am facing a disabled login button: (SOLVED) Nextcloud 12: Login button not working
If I try to log in admin with an arbitrary password on https://cloud.familycliff.co.uk, I just get back to the login screen, without any error message.
Is that the problem you are facing?
Forgot to ask: Did you look in data/nextcloud.log?