Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/27f993004beae8a1ca06c83b0a1432bd.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563