Vaadin spreadsheet

I am trying to use Vaadin spreadsheet version 3.0.0.alpha2 with Vaadin 8.

Somehow css does not compile properly and I see result as seen in the picture.

My theme compile looks like this.

        <plugin>
            <groupId>com.vaadin</groupId>
            <artifactId>vaadin-maven-plugin</artifactId>
            <version>${vaadin.version}</version>
            <dependencies>
                <dependency>
                    <groupId>xml-apis</groupId>
                    <artifactId>xml-apis</artifactId>
                    <version>1.4.01</version>
                </dependency>
            </dependencies>
            <configuration>
                <extraJvmArgs>-Xmx2G</extraJvmArgs>
                <theme>mytheme</theme>
            </configuration>
            <executions>
                <execution>
                    <goals>
                        <goal>resources</goal>
                        <goal>update-theme</goal>
                        <goal>update-widgetset</goal>
                        <goal>compile</goal>
                        <goal>compile-theme</goal>
                    </goals>
                </execution>
            </executions>
        </plugin>

Any ideas?
image.png