The core-js error is usually caused by an update or change in the current core-js version. A quick fix is usually to change the core-js version in package.json to the latest which is @3.15.2 or whichever is right now.
quick fixes you can do
- copy the code in this github repo and paste in the file directory in node modules.
- run npm clear cache. Add --force add the end if necessary.
- Close all IDE instances if any error still persists.
- run npm i firstname.lastname@example.org
Hope this helps.