Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/23eb2a54f3c47feed0b317847f78e3c1.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563