Vaadin can't find my themes.

I've got below error:
INFO: Requested resource [/VAADIN/themes/mytheme/styles.css] not found from filesystem or through class loader. Add widgetset and/or theme JAR to your classpath or add files to WebContent/VAADIN folder.

I'm using intelij.
Here is my folder structure:

My mytheme.scss:

@import "../valo/valo.scss";
@mixin mytheme {
    @include valo;
    .v-button {
        color: blue;
        background: yellow;
    }
}

My styles.scss:

@import "mytheme.scss";
@import "addons.scss";
.mytheme {
    @include mytheme;
    @include addons;
}

I have compiled scss like in docs https://vaadin.com/docs/-/part/framework/themes/themes-compiling.html#themes.compiling.maven

I attach my sources and pom.xml becouse im not sure if the above is enough.