Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/33cb05f9e3ee9e5bbc7b9d4c80f22db3.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563