Did you see this post from earlier? Included grav-logo.svg missing on extending theme
pamtbaau wrote:
If the myquark.yaml is defined incorrectly, e.g. incorrect prefixes name, the Quark theme is not executed. ( /user/themes/mytheme/mytheme.yaml )
If file myquark.php is not present, the Quark theme is not executed.
If name of class in myquark.php is defined incorrectly, the Quark theme is not executed.
Sorry I am not more help… Just starting with Grav myself a couple days ago. I am trying to learn how to troubleshoot issues so I can use this for projects knowing that I can support it.