Never 'shoot in the dark' with asset symbols, or else you may accidentally open a trade that you do not want.

Symbols can always be looked up in the broker's platform. Even is nothing else is documented, the symbols are, obviously, otherwise you could not trade.

If you're not making progress, you can contact support with the credentials to your demo account, and we'll look into that. Brokers occasionally change their API, and the Saxo plugin was developed about 2 years ago.