Your automation is referring to an input_select called hass_themes (with an S), but the code you have posted is an input_select called hass_theme (without an S).
I can’t say if your yaml is out because you haven’t used a code block so I can’t see the formatting, but a few general notes I have gained from playing with themes over the last few months…
1 - every time you add a new theme, restart HA and do a ctrl+f5 in your browser
2 - go in to the configuration tab and manually select the theme to make sure it’s working.
3 - if you’re planning on automating theme changes ensure you put it back to ‘backend selected’, otherwise it will just stay on the last one you manually picked.
I have an automation that manages my themes thus…
During daytime - default
Evening - midnight theme
Overnight - Darkcyan theme
Alarm is set - Darkred theme
Maintenance mode is on - Darkorange theme,
Thanks for the reply. So I fixed the (s) and restarted Hassio but now when I select any theme I get theme not found in the log. I’m not worried about the automation at this point would just like to get the manual select working. Being very new to HA not sure about you reference to the “configuration tab” and how to use it. I have configured Automation via this but not sure how to use it to test if a theme works