Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/293a9efe0b17f0a54a6d45e3dab70e05.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563