Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/b99a62dc61f8a808c01146d6e5156511.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563