Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/ec16da7f2e89222c101e68a7d26ddce2.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563