could not be opened in append mode code example
Example 1: could not be opened in append mode: failed to open stream: Permission denied
chmod -R 775 storage
chmod -R 775 bootstrap/cache
Example 2: could not be opened in append mode: failed to open stream: Permission denied
sudo chown -R $USER:www-data storage
sudo chown -R $USER:www-data bootstrap/cache
Example 3: could not be opened in append mode failed to open stream permission denied
Reference link if giving a permission doesn't solved your issue
https://www.digitalocean.com/community/questions/the-stream-or-file-var-www-html-myscipt-storage-logs-laravel-log-could-not-be-opened-failed-to-open-stream-permission-denied
Example 4: could not be opened in append mode
chmod -R 777 storage