Plugin 'org.apache.maven.plugins:maven-jar-plugin:' not found

I have the problem described in the title but the plugin does its duty. The files are excluded from the jar file. The only detail I notice is that the ConfigureTomcatConHttps$1.class file is not removed. As I understand it, $1.class files are relative to anonymous inner classes. If I remove a file from the project I expect to remove the anonymous inner class as well but this is just a minor detail that doesn't cause me any problems. If the plugin works, it means it exists and it is doing its job, so why is IntelliJ marking the code in red for me?

Thank you

<plugins>
    <plugin>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-maven-plugin</artifactId>
    </plugin>
    <plugin>
        <groupId>org.apache.maven.plugins</groupId>
        <artifactId>maven-jar-plugin</artifactId>
        <configuration>
            <excludes>
                <exclude>/it/applicazionijava/gestioneutenti/CrittografarePassword.class</exclude>
                <exclude>/it/applicazionijava/gestioneutenti/autenticazione_spring_security/ConfigurazioneTomcatConHttps.class</exclude>
                <exclude>/application-sviluppo.properties</exclude>
                <exclude>/funzioni.sql</exclude>
            </excludes>
        </configuration>
    </plugin>
</plugins>

Plugin 'org.apache.maven.plugins:maven-jar-plugin:' not found:241
Plugin 'org.apache.maven.plugins:maven-jar-plugin:' not found:242