Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/47e0d9828ba9bf3f7b743e5e09ad0de2.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563