Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/b0f6140649e48a0c07d270136d5d9fcf.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563