Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/cd35c3e99077be87c015d5c7494b1cf3.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563