I just Solved mine with the "unresolved plugin: 'org.apache.maven.plugins:maven-compiler-plugin:3.9.9'

What you have to do is go the the .m2 file then rename the repository as "old repo" or you can delete it then go to the intelliJ then reload all maven project which it recreates the "repository" file to the .m2 and the IDE will automatically download the plugins! so hopefully this will resolve your issue!