get service pack 4(6.5.4), it should fix your issue. 

I found this and I applied to my wknd and it worked for me:https://youtu.be/lKWHsVh1hRA

I found the fix here and I applied it to my wknd, and the byline issue went away.How to fix packages cannot be resolved issue in AEM archetype project - YouTube Hope it helps.

I m still trying to figure out what and where the issue is.

Yes, I was talking about pom.xml file I updated.

I am using VSCode, I experienced the same error, the parent POM already updated to core 2.4.0.When I built with mvn, there is no error.I wonder what else can I look at? How would I know which version of core should be used?Thanks in advanced.