Unresolved plugin: 'org.springframework.boot:spring-boot-maven-plugin:2.3.4.RELEASE'

As an AI language model, I don't have enough context to provide a specific solution for your issue with the `org.springframework.boot:spring-boot-maven-plugin:2.3.4.RELEASE` plugin. However, here are some general tips to help you resolve the issue:

1. Check your Maven settings: Make sure that your Maven settings are configured correctly and the plugin is specified in the pom.xml file. You can also try updating your Maven version.

2. Check your internet connection: Ensure that your internet connection is stable and the necessary dependencies are downloaded successfully.

3. Check for conflicts: There may be conflicts with other plugins or dependencies that are preventing the plugin from being resolved. Try removing any unnecessary plugins or dependencies.

4. Check for compatibility: Make sure that the plugin version is compatible with your Spring Boot version. You can refer to the Spring Boot documentation for compatibility information.

5. Try cleaning and rebuilding your project: Sometimes, cleaning and rebuilding the project can resolve issues with the plugin.

If none of the above solutions work, you can try searching for specific solutions or asking for help on forums or communities dedicated to Spring Boot and Maven.