Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/34b4100fe3a0c7b4abccdb77b056f9a7.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563