Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/144b5b64c7e28281545e767c5cd5d735.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563