Plugin 'maven-assembly-plugin:' not found

It seems that you are trying to use the Maven Assembly Plugin in your project, but the plugin is not found.

Here are a few things you can try:

1. Make sure that you have added the plugin to your project's `pom.xml` file. You can do this by adding the following code to the `<plugins>` section:

<plugin>
    <groupId>org.apache.maven.plugins</groupId>
    <artifactId>maven-assembly-plugin</artifactId>
    <version>VERSION_NUMBER_HERE</version>
</plugin>

Replace `VERSION_NUMBER_HERE` with the appropriate version of the plugin that you want to use.

2. Check that you have an internet connection and that you can access the Maven Central Repository. The plugin may not be downloaded properly if there are issues with your network.

3. Try running the command `mvn clean install` in your project directory to force a fresh build of your project and redownload any missing dependencies.

I hope this helps! Let me know if you have any other questions.