Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/64c75f58b2d040f2978e0bce916ad40f.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563