Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/71235861b67c89fc5566ead4b2f0f6e5.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563