[SOLVED]Theme Background not working with https

Hi all,
Hope this is the right place to ask.
I am using a theme that is using a background that is defined in the theme file.

background-image: 'center / cover no-repeat url("/local/day_ha_background.jpg") fixed'

When I connect using the ip address of HA The background is correctly displayed.
Recently I install traefik and use my own domain with let’sencrypt.

When I connect via https then the background stays white whatever I do.

Is there any logs I should be looking to see what the problem is?

I found the problem.

For some reason the theme in my user setting was set to default rather than backend-select (as it was before)

Once updated my automation is able to change the theme as required