Background - I have been maintaining a Drupal site for years, but I am a casual that doesn't really know much. I started on Drupal 8 and survived a migration over to Drupal 10 and switched themes at that point to "Drupal8 W3CSS Sub-theme". I get by but ultimately I don't really know what I am doing.

Today I saw an update to the theme I am using and I foolishly installed it with composer. I now get the error:

Symfony\Component\DependencyInjection\Exception\ServiceNotFoundException: You have requested a non-existent service "Drupal\drupal8_w3css_theme\Hook\Drupal8W3cssThemeHooks". in Drupal\Component\DependencyInjection\Container->get()

Been googling and using AI recommendations for a fix but so far no luck sorting it out. I decided to then install the Solo theme which is the latest generation of W3CSS. I installed it fresh and switched over, and that resulted in the following error instead:

Symfony\Component\DependencyInjection\Exception\ServiceNotFoundException: You have requested a non-existent service "Drupal\solo\Hook\SoloThemePreprocessHooks". in Drupal\Component\DependencyInjection\Container->get(

I have cleared the cache with drush each time and verified that these files do exist where you would expect them to be. I have also used composer to check for outdated components and none are red, although a number are yellow.

If I switch to a completely different theme then my site loads, although it is very malformed, so I am hoping to get one of the above themes working rather than having to do implement a completely new theme.

Any advice for me?