php artisan not responding after Laravel 7 upgrade

Hello all,

I am in my local environment and just upgraded to laravel 7. However, php artisan commands no longer works. I even deleted the vendor folder and reinstalled all packages. It seems composer is installing all packages, but at the end it spits out below error message;

Script @php artisan package:discover --ansi handling the post-autoload-dump event returned with error code 255

Any ideas on how I can resolve this? I am using php 7.2.18.