It sounds like you renamed the “Default” deck. That probably seemed practical at the time – but the “Default” deck has some special (hidden) properties, and it shouldn’t be shared into other collections.
To fix it in your collection –
Rename your deck to Default [spelled exactly like that].
Click “Create Deck” to make a new deck with the name you wanted.
In Browse, select all the cards in the “Default” deck and move them to your new deck with Cards > Change Deck.
[Watch in amazement as the Default deck disappears, and you never have to think about it again.]
Check that your new deck is using the correct Options preset.
Once you sync those changes with AnkiWeb, you should be able to share you deck just fine.
My deck has a name, not Default. Anyway I want to follow your suggestion. I looked at the Anki manural, but it doesn’t say how to move cards. I have more than 700 cards. How to select all of them?