We also need to set correct permissions for storage files in the server. So, we need to give a write permission in the storage directory as follows:

$ chmod -R 777 ./storage ./bootstrap

or you may use

$ sudo chmod -R 777 ./storage ./bootstrap

For windows

Make sure you are an admin user on that computer with writeable access

xampp\htdocs\laravel\app\storage needs to be writable

The NORMAL way to set permissions is to have your files owned by the webserver:

sudo chown -R www-data:www-data /path/to/your/root/directory