Icons in Vaadin 8

I have i customized valo based Theme. When I try do display an Icon it renders with

<span class="v-icon Vaadin-Icons"></span>

and displays nothing. Has anyone an idea what I'm getting wrong?

I have something like this:

<span class="v-icon v-icon-download" style="font-family: Vaadin-Icons;"></span>

Please, check if you have the latest vaadin-icons in your maven:

<dependency>
           <groupId>com.vaadin</groupId>
           <artifactId>vaadin-icons</artifactId>
           <version>3.0.1</version>
        </dependency>

my addons.scss

/* This file is automatically managed and will be overwritten from time to time. */
/* Do not manually edit this file. */

/* Provided by vaadin-icons-3.0.1.jar */
@import "../../../VAADIN/addons/vaadin-icons/vaadin-icons.scss";


/* Import and include this mixin into your project theme to include the addon themes */
@mixin addons {
    @include vaadin-icons;
}

my styles.scss

@import "mytheme.scss";
@import "addons.scss";

// This file prefixes all rules with the theme name to avoid causing conflicts with other themes.
// The actual styles should be defined in mytheme.scss

.mytheme {
  @include addons;
  @include mytheme;

}

Vaadin maven plugin conf:

<plugin>
                <groupId>com.vaadin</groupId>
                <artifactId>vaadin-maven-plugin</artifactId>
                <version>8.0.1</version>
                <executions>
                    <execution>
                        <goals>
                            <goal>update-theme</goal>
                            <goal>update-widgetset</goal>
                            <goal>compile</goal>
                            <!-- Comment out compile-theme goal to use on-the-fly theme compilation -->
                            <goal>compile-theme</goal>
                        </goals>
                    </execution>
                </executions>
            </plugin>

Thanks Roman, you gave me a good start today :)