Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/b701f6d9d81d15521f676c66d76f68c7.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563