Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/a9a8bb9b6cbbba97375730b4b3e46e4d.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563