I also get a similar error on IntelliJ after loading maven changes.

Cannot find project Scala library 2.12.10 for module XXX

For me, the issue is fixed after adding the following dependency in pom.xml

<dependency>
    <groupId>org.scala-lang</groupId>
    <artifactId>scala-library</artifactId>
    <version>2.12.10</version>
</dependency>