For some reason I had a typo in the maven-checkstyle-plugin

            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-checkstyle-plugin</artifactId>
                <configuration>
                    <configLocation>checkstyle.5.0.xml</configLocation>
                </configuration>
            </plugin>

where I used the wrong name for the checkstyle file.
However under Project Properties/SQE/Checkstyle NB told me that NB is 'Using Maven Checkstyle plugin configuration found in the project'. 

I only found out about this error since the maven goal checkstyle:check threw an error.

Nb also should report (eg. in the project properties) that there is a problem with the configuration, eg the checkstyle file could not be found