Hi Geoff,
The login button can be switched off in some themes, which can be good in some ways as it prevents confusion for users visiting the site, but it can make it a bit trickier for administrators.
If you are struggling to log in or admin the site, then in the URL bar go directly to your site's homepage URL and add /admin on the end.
So for example for the demo site it would be https://e-voice.org.uk/demosite/admin
Or for sites with a custom URL go to: https://my.website.url/admin
The site will ask you to log in if you haven't already done so.
If you get a permission denied error after logging in then it means you have logged in with an account that doesn't have admin permissions on the site.
Thanks
Joe