Laravel 5.7.20
Horizon 3.0.0
After installing Horizon 3.0.0, i ran php artisan horizon:install
start horizon by php artisan horizon and go to http://localhost/horizon/dashboard, I got Error Exception, Unable to local Mix fie: /app.css (View:..../vendor/laravel/horizon/resources/views/layout.blade.php)
php artisan horizon:install publishes assets without 'force' flag, which is why your assets are not being overwritten.
use the php artisan horizon:assets command instead.
I had the same issue.
See https://github.com/laravel/horizon/issues/525#issuecomment-467952910
Most helpful comment
php artisan horizon:installpublishes assets without 'force' flag, which is why your assets are not being overwritten.use the
php artisan horizon:assetscommand instead.