ERROR in ngcc is already running at process with id xxxx [closed]
Try deleting your ngcc_lock_file in the path: node_modules/@angular/compiler-cli/ngcc/ngcc_lock_file Or for Angular 9, the lock file to delete is: node_modules/@angular/compiler-cli/ngcc/__ngcc_lock_file__ I had the same issue and I and deleted that file and it started working for me.